Which
Which is an English pronoun and determiner. As an interrogative pronoun or determiner, it is used in questions to specify one or more items from a limited set of possibilities. For example: "Which book did you choose?" or "Which of these is yours?"[1] As a relative pronoun, which introduces a relative clause that provides information about a thing or situation previously mentioned, often set off by commas in non-restrictive clauses. For example: "The car, which was red, broke down." It cannot replace "that" in non-restrictive clauses or after prepositions.[1][2] Which also functions as a determinative, modifying a noun to indicate selection from alternatives, as in "Choose which option suits you best." Its usage is detailed further in the grammatical functions section.Grammatical Functions
Interrogative Pronoun
As an interrogative pronoun, "which" is used in English to inquire about a specific item, person, or option from a limited or known set of alternatives, often implying selection among possibilities.[3] Unlike "what," which seeks open-ended identification, "which" presupposes prior context or enumeration, such as choices presented in a list.[4] This function positions "which" alongside other wh-pronouns like "who" and "what" in forming direct questions.[3] In terms of syntax, "which" can occupy various positions within a question, typically fronted via wh-movement—a process where the interrogative element displaces to the sentence-initial position to signal the query.[5] As a subject, it appears as in "Which came first, the chicken or the egg?" where it directly inquires about the agent.[3] In object position, the structure involves auxiliary inversion, as in "Which book do you prefer?" with "which" moving from the verb's complement to the front.[6] For prepositional objects, it follows the preposition, which also fronts, yielding forms like "In which city were you born?"—a pied-piping construction common in formal English.[5] These examples illustrate wh-movement's role in English interrogatives, ensuring the pronoun initiates the clause while preserving underlying semantic relations.[6] Historically, "which" derives from Old English hwīlc (or variants like hwælc), a compound of hwā ("who" or "what") and līc ("body" or "form"), literally meaning "of what kind."[7] This interrogative form, used to specify among options, persisted through Middle English, where parallel spellings like hwelc faded by the 15th century, solidifying the modern pronunciation and spelling amid broader phonological shifts in wh-words.[7] In indirect questions, "which" embeds within a larger clause without inversion or do-support, maintaining declarative word order to report or ponder a query, as in "I wonder which option is best" or "She asked which route we should take."[2] This usage softens direct interrogation, common in polite or reported speech.[2] While "which" also serves as a relative pronoun to introduce descriptive clauses, its interrogative role distinctly focuses on eliciting selection in questions.[3]Relative Pronoun
In English grammar, "which" functions as a relative pronoun to introduce a relative clause that modifies a noun or noun phrase, typically referring to non-human antecedents or specified entities, thereby providing descriptive or identifying information about the antecedent.[8] This usage connects the clause to the main sentence, embedding additional details that relate back to the noun it describes, such as in the example: "The book which I read was excellent."[9] The relative pronoun "which" appears in two primary types of clauses: restrictive and non-restrictive. Restrictive clauses, which convey essential information necessary to identify the antecedent, do not use commas and can employ "which" (though "that" is often preferred in American English). For instance, "The report which arrived yesterday requires immediate review" specifies which report among potentially many.[9] In contrast, non-restrictive clauses provide supplementary, non-essential information and are always set off by commas, exclusively using "which" to introduce them; an example is "The report, which arrived yesterday, requires immediate review," where the timing adds detail but does not define the report.[8] Syntactically, "which" can serve as the subject, object, or complement within the relative clause. As a subject, it acts as the performer of the clause's verb, as in "The car which broke down delayed our trip," where "which" refers to the car initiating the action.[8] In object position, it receives the action, often following the verb or preposition, such as "The car which I bought last year is reliable."[9] For possessive or prepositional constructions, "which" follows a preposition to indicate relation or location, like "The house in which we lived for years was sold," or it pairs with "whose" for direct possession, as in "The company whose policies changed faced backlash."[8] Examples of "which" in complex sentence structures illustrate its versatility in nesting clauses or combining with other elements. In a restrictive context within a compound sentence: "She visited the museum which housed ancient artifacts and admired the exhibit that inspired her research." Here, "which" identifies the specific museum.[8] For non-restrictive use in a more intricate setup: "The novel, which critics praised for its innovative plot and which sold over a million copies, transformed the author's career." This embeds two parallel non-restrictive clauses for added description. The evolution of "which" as a relative pronoun traces back to Old English, where it derived from "hwilc" (meaning "of what kind"), initially functioning as an interrogative adjective and pronoun with demonstrative qualities.[11] In late Old English and Middle English periods (roughly 11th–15th centuries), it shifted toward relative use by analogy with interrogative forms, replacing earlier inflected demonstratives like "se þe" in subordinate clauses, and solidified as a standard relative pronoun by early Modern English.[12] This development allowed for more flexible clause embedding, reflecting broader syntactic changes in the language.[11]Determinative Role
In English grammar, "which" serves as a wh-determiner when positioned before a noun to denote selection from a predefined or limited set of alternatives, forming phrases such as "which book" or "which path." This role distinguishes it as an interrogative or relative element that specifies particularity within a restricted domain, often implying prior context or options known to the speaker and listener.[13] This determinative function appears prominently in interrogative constructions, where it initiates questions focused on choice, as in "Which color do you like?" to elicit a selection from available options. In relative contexts, it modifies a head noun or substitute to highlight specificity, for example, "the color which appeals to you," thereby linking the noun to a defining characteristic from a limited range. Unlike indefinite determiners like "a" or "some," which convey generality or non-specific reference without presupposing alternatives, "which" underscores a deliberate pick from an identifiable subset, adding a layer of precision and exclusivity to the noun phrase.[14][15][16] The historical trajectory of "which" as a determinative traces to Old English "hwilc," a compound interrogative adjective meaning "what kind of," which already functioned to qualify nouns by indicating choice or quality from possibilities. Through Middle English, this form persisted with minor phonetic shifts, and by Early Modern English (roughly 1500–1700), it had fully entrenched its modern determinative role, appearing in texts to select from known entities, as evidenced in relative and continuative clauses modifying nouns. This evolution reflects a continuity in its interrogative essence while adapting to the expanding noun phrase structures of the period.[17][18] In declarative sentences, "which" as a determiner facilitates instructions or descriptions involving selection, such as "Choose which path leads to the village," where it directs attention to one option among delineated routes. This usage maintains the emphasis on limitation inherent to its wh-interrogative origins, contrasting with its standalone pronominal forms in other grammatical contexts.[14]Historical Development
Etymology from Proto-Indo-European
The English interrogative and relative pronoun "which" traces its origins to the Proto-Indo-European (PIE) root *kʷo-, an interrogative-indefinite stem that formed pronouns denoting "who," "what," or "which." The nominative singular masculine/neuter form *kʷís specifically served as an interrogative pronoun with these meanings, part of a broader paradigm built on *kʷi- (for nominative and accusative cases) and *kʷe- (for other cases), paralleling anaphoric stems like *i- and *e-.[7][19] This reconstruction relies on the comparative method in historical linguistics, which identifies regular sound correspondences and shared innovations across Indo-European languages to posit ancestral forms. Cognates of *kʷís appear widely: in Latin as quis (nominative "who? what?"), in Ancient Greek as tis (τίς, "who? what? which?"), in Sanskrit as kaḥ (कः, "who?"), in Old Irish as cía ("who?"), and in Oscan (an Italic language) as pis ("who?"). These forms demonstrate the preservation of the labiovelar kʷ in centum languages (like Latin and Greek) and its palatalization to k in satem languages (like Sanskrit and Iranian).[19][20] Linguistic evidence further supports *kʷís as an original interrogative that grammaticalized into relative and indefinite functions in many branches, a common typological pathway where questions about identity evolve into modifiers specifying referents. This is evidenced by synchronic distributions in early attested languages and diachronic shifts, such as the merger of interrogative and relative roles in older Indo-European texts.[20][21] Within the Germanic subfamily, the PIE stem developed into Proto-Germanic *hwilīkaz ("what kind of?"), a compound of hwaz ("who? what?," from PIE *kʷos, the oblique stem) and līkaz ("like, of the same form," related to body or appearance). This compound structure emphasized selection or specification, setting the stage for its adoption in early Germanic dialects.[7]Evolution in English
In Old English, the interrogative and relative pronoun corresponding to modern "which" appeared in forms such as hwīlc (West Saxon) or hwǣlc (Anglian), a compound of hwī- (from the interrogative base related to "who") and -līc ("form" or "body"), literally denoting "of what form" or "what kind."[7] This structure reflected its role in specifying type or kind within a set, and it inflected for case (nominative, accusative, genitive, dative), gender (masculine, feminine, neuter), and number (singular, plural), aligning with the synthetic grammar of the period.[22] Building on Proto-Indo-European roots traced to interrogative particles like kwo-, these forms evolved through Proto-Germanic hwī-līkaz into the distinctly English variants.[7] During the Middle English period (c. 1100–1500), the word simplified to "which" amid sweeping phonological reductions and the decline of the inflectional system following the Norman Conquest, which accelerated the shift toward analytic syntax reliant on word order and prepositions.[23] Case endings largely disappeared, leaving the uninflected form dominant by the 14th century, as evidenced in Chaucer's works where "which" served both interrogative and relative functions without gender or number distinctions.[7] This leveling eliminated dialectal variants like the Old English hwylc, standardizing the pronunciation closer to /wɪtʃ/ and broadening its use in compounds, though parallel Old English forms vanished entirely by the 15th century.[7] In Early Modern English (c. 1500–1700), the introduction of printing by William Caxton in 1476 significantly influenced the standardization of "which," as his press favored the orthography of the London-based East Midlands dialect, promoting consistent spelling and reducing regional variations in printed texts.[24] Caxton's editions, such as his 1484 printing of the Aesop fables, helped fix "which" in its contemporary form, minimizing earlier inconsistencies and aiding its integration into the emerging standard English grammar amid the Great Vowel Shift and lexical expansions from Renaissance scholarship.[25] The 20th century marked a notable shift in attitudes toward "which," with prescriptive grammarians like Henry Watson Fowler in A Dictionary of Modern English Usage (1926) advocating its limitation to non-restrictive relative clauses (preceded by commas), reserving "that" for restrictive ones to enhance clarity—a rule popularized earlier by the Fowlers' The King's English (1906) and reinforced in American guides like Strunk and White's The Elements of Style (1918 onward).[26] This prescriptive stance sparked ongoing debates with descriptive linguists, who emphasized historical evidence of "which" in both clause types (e.g., in Shakespeare and Austen) and argued the distinction was an artificial 20th-century innovation lacking empirical basis in natural usage.[27] These tensions highlighted broader conflicts between rigid rule-making and observational linguistics, influencing style guides into the late 20th century.[26]Usage Rules and Examples
In Restrictive and Non-Restrictive Clauses
In English grammar, "which" serves as a relative pronoun introducing relative clauses, which modify a noun or pronoun known as the antecedent. Restrictive relative clauses, also called defining clauses, provide essential information that identifies or specifies which particular antecedent is being referred to, thereby narrowing the scope of the reference. These clauses do not require commas to set them off from the rest of the sentence. For instance, in the sentence "The policies which favor renewable energy will succeed," the clause "which favor renewable energy" restricts the meaning to only those policies meeting that criterion, distinguishing them from others that do not.[29] Non-restrictive relative clauses, or non-defining clauses, offer additional, non-essential information about the antecedent, elaborating on it without limiting its scope. Such clauses are always set off by commas, signaling their parenthetical nature. An example is "The policies, which favor renewable energy, will succeed," where the clause "which favor renewable energy" adds supplementary detail but could be removed without altering the sentence's core meaning, as it applies to all the policies in question. This punctuation distinction ensures clarity, as omitting commas in non-restrictive clauses could imply a restrictive interpretation. According to the Chicago Manual of Style, nonrestrictive clauses introduced by "which" must be enclosed in commas, while restrictive clauses introduced by "which" (more common in British English than American) lack them.[29][30] The semantic impact of these clause types is profound: restrictive uses of "which" create precision by excluding alternatives, fostering a sense of selection, whereas non-restrictive uses enrich description without implication of exclusion, often conveying a more narrative or explanatory tone. In British English, "which" frequently appears in both clause types, as seen in classic literature; for example, the King James Bible employs a restrictive "which" in Matthew 22:21: "Render therefore unto Caesar the things which are Caesar's; and unto God the things that are God's," where the clause specifies the particular things owed to each authority. In journalism, non-restrictive "which" clauses commonly provide context; The Guardian illustrates this in "The Guardian, which I read every day, is the paper that I admire above all others," where the clause adds personal detail without defining the paper's identity.[31][32] These conventions, while flexible across dialects, underscore "which"'s versatility in clause construction, with style guides like the Chicago Manual emphasizing comma usage to delineate essential from incidental information.[29]Common Errors and Prescriptive Guidelines
One common error involves using "which" to introduce restrictive relative clauses in American English, where "that" is the preferred relative pronoun for essential information that defines the antecedent. According to the Associated Press Stylebook, writers should "use the word that and never use which to introduce an essential clause," as "which" is reserved for nonessential clauses set off by commas.[33] For example, in a 2011 news article draft, an editor corrected "The policy which affects low-income families will change next year" to "The policy that affects low-income families will change next year" to adhere to this rule and clarify the restrictive nature of the clause.[33] In British English, however, "which" is more flexibly permitted in restrictive clauses alongside "that," without strict prohibition. New Hart's Rules: The Oxford Style Guide states that "in restrictive relative clauses either which or that may be used in British English," allowing for stylistic variation while maintaining clarity. This difference can lead to inconsistencies in international publications; for instance, a BBC article might retain "The book which I recommended is out of print," whereas an American counterpart would revise it to "The book that I recommended is out of print" per AP guidelines.[34] Another frequent issue is the dangling modifier or ambiguous antecedent with "which," where the pronoun fails to clearly refer to a specific noun, creating confusion about what is being modified. Grammar authorities emphasize that "which" must refer to a precise antecedent, such as a single noun or noun phrase, rather than an entire sentence or vague idea, to avoid misinterpretation.[35] A classic example from edited texts is the ambiguous sentence "She completed the report quickly, which was impressive," where "which" could refer to the completion, the report, or the speed; it is corrected to "She completed the report quickly, an impressive feat" or "Completing the report quickly was impressive" to eliminate the ambiguity.[36] In a real-world case from a business memo analyzed by Purdue OWL, "The merger was approved by the board, which surprised everyone" was revised to "The merger, which surprised everyone, was approved by the board" to ensure "which" unambiguously modifies "merger."[37] Overuse of "which" in complex sentences or lists can also introduce ambiguity, particularly when multiple clauses create unclear references or bloated prose. Style guides recommend limiting "which" to nonrestrictive uses and restructuring sentences to avoid chaining multiple "which" clauses, which can obscure meaning in intricate structures.[38] For instance, in a lengthy academic abstract, an original sentence like "The study examined factors A, B, and C, which influenced outcomes, which varied by region, which included urban areas" was streamlined to "The study examined factors A, B, and C, which influenced outcomes that varied by region, including urban areas" to reduce redundancy and clarify connections.[36] This correction, drawn from peer-reviewed editing examples, prevents reader fatigue and ensures precise communication in dense writing.[37]Comparisons with Similar Words
Which versus That
In English grammar, the relative pronouns "which" and "that" are both used to introduce relative clauses, but their application differs based on whether the clause is restrictive (essential to identifying the antecedent) or non-restrictive (providing supplementary information). Restrictive clauses, which narrow down or define the noun they modify, typically employ "that" and do not use commas, as in "The book that I read yesterday was fascinating." This usage applies neutrally to both human and non-human antecedents. In contrast, non-restrictive clauses, which add non-essential details and are set off by commas, require "which," as in "The book, which I read yesterday, was fascinating."[38][9] American English exhibits a strong stylistic preference for reserving "that" exclusively for restrictive clauses and "which" solely for non-restrictive ones, a convention reinforced by major style guides. For instance, The Elements of Style by Strunk and White states that "that" is the defining or restrictive pronoun, while "which" is nondefining or nonrestrictive. Similarly, The Chicago Manual of Style (17th edition) advises using "that" for restrictive clauses involving things and "which" for non-restrictive ones. An illustrative pair of examples highlights this: "The dog that barked kept me awake" (restrictive, identifying which dog) versus "The dog, which barked, kept me awake" (non-restrictive, assuming the dog is already specified). In British English, however, "which" is more flexibly accepted in restrictive clauses without commas, though "that" remains common; this variance reflects less rigid adherence to the American distinction.[9][39][40] Historically, "that" emerged as the predominant relative pronoun through the merger of its demonstrative origins with relative functions, a process traceable to Old English where relatives were often formed by combining demonstratives like "þæt" (that) with the particle "þe" (which evolved into a relative marker). By the Middle English period, around eight hundred years ago, "that" had solidified as the standard relative pronoun for both persons and things, while "which" (derived from Old English "hwilc," meaning "what sort") gained prominence for non-restrictive or interrogative-like uses. This development contributed to the modern interplay, where "that" handles essential definitions efficiently, avoiding the potential ambiguity of "which" in restrictive contexts.[41][42]Which versus Who
In English grammar, the relative pronouns "who" and "which" are distinguished primarily by animacy: "who" is used to refer to people or other animate beings, serving as either the subject or object of a clause, while "which" refers to inanimate objects, animals without personal reference, or collective entities treated as non-personal.[43][8] This distinction ensures clarity in identifying the referent's nature within relative clauses.[44] For example, in referring to a person, one says "The doctor who treated me was kind," where "who" acts as the subject, whereas for an object, "The machine which malfunctioned caused delays" employs "which" as the subject.[43] Similarly, as objects, "The colleague whom I met" uses the objective form of "who," contrasted with "The report which I reviewed."[8] An exception arises with collective nouns denoting groups of people, where "which" is acceptable, particularly in formal contexts, treating the group as a singular entity; for instance, "The committee which approved the proposal consists of experts."[43][44] Prescriptive guidelines in modern standard English strongly advise against using "which" to refer to individual humans, reserving it for non-personal antecedents to maintain precision, though historical usage in Early Modern English, such as in Shakespearean works or the King James Bible ("Our Father which art in heaven"), demonstrated greater flexibility.[8][45] In formal writing, adherence to "who" for people is emphasized.[43] Dialectal and informal variations in English may occasionally blur this boundary, with "which" appearing in non-standard speech for people, though such usage is not recommended in edited prose.[44] In interrogative forms, the pattern holds similarly, with "who" for people and "which" for things or groups.[2]Non-Linguistic Uses
In Computing
In Unix-like operating systems, thewhich command is a utility that identifies the full path of an executable file as resolved by the shell when searching the directories listed in the PATH environment variable.[46] For instance, running which ls on a typical system outputs /bin/ls, indicating the location of the ls executable that would be invoked.[46] This functionality aids users and scripts in verifying the location of commands without executing them, promoting portability and debugging in shell environments.
The basic syntax is which [options] [--] programname [...], where multiple program names can be specified, and the command prints the full path for each matching executable found first in PATH.[46] Common options include -a or --all to display all matches in PATH rather than just the first one, and --version to show version information.[46] The command originated in early Unix distributions, first appearing in 3BSD developed at the University of California, Berkeley, during the late 1970s.[47] Although widely adopted across Unix-like systems, which is not part of the POSIX standard; the POSIX-specified equivalent for path resolution is the shell builtin command -v, which performs a similar search and is mentioned in the POSIX rationale as a standardized alternative to historical utilities like which.[48]
Alternatives to which include the whereis utility, which locates the binary, source, and manual page files for a command and is defined in the POSIX standard, and the type builtin available in many shells like Bash, which describes how a command would be interpreted (e.g., alias, function, or file path). In shell scripts, which is often used for conditional execution, such as checking if a tool is available before proceeding:
This example demonstrates path verification in a script, ensuring compatibility across environments whereif which git > /dev/null; then echo "Git is installed at $(which git)" else echo "Git not found in PATH" fiif which git > /dev/null; then echo "Git is installed at $(which git)" else echo "Git not found in PATH" fi
git might reside in different locations like /usr/bin/git or /usr/local/bin/git.