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Stop

Stop is a fundamental English meaning to cease motion, action, or operation, or to obstruct or close something, and as a , it denotes a cessation, a halting , or a brief pause. Its etymology derives from stoppen and -stoppian, signifying to block or stuff an , ultimately from West Germanic roots linked to stuppare (to stuff with tow), with first attested uses in the for the and for the . Beyond core senses of halting progress or preventing passage, "stop" holds specialized meanings in domains such as , where it refers to a set of organ pipes or a altering ; , for consonants involving complete closure of the breath stream; and , for any impediment to motion. These usages underscore its role in denoting interruption or , with synonyms like cease or halt varying in connotations of finality or abruptness.

Places and infrastructure

Facilities and locations

Bus stops serve as designated for public transportation, typically comprising marked areas, , and often shelters to protect waiting passengers from . These facilities are strategically placed along routes to and , with optimal spacing of 400 to 1,000 feet in areas to minimize walking time while maintaining speed. Modern iterations incorporate amenities like benches, lighting, trash receptacles, and digital displays providing real-time arrival information via GPS integration, enhancing in high-traffic locations. Historically, precursor stops emerged with early services in the 1820s, evolving from simple roadside markers for horse-drawn vehicles to structured halts; for instance, the first fixed-route bus line in , , in 1824 relied on basic boarding points without dedicated shelters until later urban expansions. In the American West, and routes utilized relay stations spaced 5 to 20 miles apart for horse changes, rider rests, and mail transfers, with over 190 such sites along the 1,900-mile trail from St. Joseph, Missouri, to , operational from April 1860 to October 1861; home stations, numbering about 25, accommodated riders overnight, while swing stations focused on equine logistics. Pit stops in circuits function as specialized facilities within the pit lane, equipped with garages, fueling rigs, and workstations for rapid vehicle servicing, including replacements and adjustments that occur in under 3 seconds for elite Formula 1 teams. These areas, integral to race strategy, enable mandatory halts for safety and performance, with infrastructure designed for sequential movements to comply with regulations limiting personnel per stall. Truck stops represent key for commercial freight, offering parking for up to thousands of rigs, fueling stations, maintenance bays, and rest areas to enforce hours-of-service rules requiring 10-hour breaks after driving limits. Numbering over 2,000 major sites across the U.S., they sustain supply chains by mitigating fatigue and enabling quick repairs, with recent analyses highlighting their role as essential hubs rather than optional amenities, particularly in where shortages exacerbate delays.

Arts and entertainment

Film and television

"Bus Stop (1956) is an American romantic comedy-drama film directed by Joshua Logan, adapted from William Inge's play of the same name, and starring Marilyn Monroe as saloon singer Chérie and Don Murray as naive cowboy Beauregard 'Bo' Decker. The plot centers on Decker's infatuation with Chérie during a rodeo in Phoenix, Arizona, leading to his attempt to abduct her amid a snowstorm stranding travelers at a bus stop; the film explores themes of impulsive love and personal growth, culminating in Decker's maturation. Released on August 31, 1956, by 20th Century Fox, it received mixed to positive reviews for Monroe's performance, earning an IMDb rating of 6.3/10 from over 13,000 users and a 73% approval on Rotten Tomatoes based on 15 reviews. "Stop! Or My Mom Will Shoot (1992) is a buddy cop action-comedy directed by Roger Spottiswoode, featuring Sylvester Stallone as Los Angeles Police Sergeant Joe Bomowski and Estelle Getty as his interfering mother Tutti, who becomes involved in his investigation of a gun-smuggling ring after witnessing a murder. Released on February 21, 1992, the film grossed $70.6 million worldwide against a $15 million budget but faced critical derision for its formulaic humor and improbable plot, holding an IMDb score of 4.4/10 from 46,000 ratings. "Stop-Loss (2008), directed by Kimberly Peirce, dramatizes the U.S. military's stop-loss policy through Staff Sergeant Brandon King (Ryan Phillippe), who returns from Iraq only to be involuntarily extended for another deployment, prompting him to go AWOL and confront war's psychological toll alongside comrades. Premiering at the SXSW Film Festival on March 10, 2008, and widely released April 18, it earned a 64% Rotten Tomatoes approval from 141 reviews, praised for its anti-war message but critiqued for melodramatic execution, with an IMDb rating of 6.4/10. In television, "Bus Stop (1961–1962) was an ABC anthology drama series adapted from Inge's play, starring as café owner in the fictional town of , where episodes unfold around transient passengers' stories involving romance, crime, and moral dilemmas at a roadside . Airing 26 episodes from October 1, 1961, to March 25, 1962, it featured guest stars like and , blending suspense and human interest but achieving modest viewership and an rating of 6.8/10 from 116 users. The Twilight Zone's "A Stop at Willoughby" (Season 1, Episode 30, aired May 6, 1960) is an anthology entry written by Rod Serling, starring James Daly as advertising executive Gart Williams, who, overwhelmed by career stress, dreams of an idyllic 19th-century town called Willoughby during commuter train naps, blurring reality and escape in a tale of midlife crisis. Serling cited it as his favorite first-season story; it holds an 8.5/10 IMDb rating from 5,300 votes for its poignant commentary on modern alienation.

Music

"Stop! In the Name of Love" is a 1965 single by , written and produced by Motown's team; it topped the for two weeks and reached number one on the . The song's lyrics urge halting romantic arguments to preserve a relationship, blending pop-soul with orchestral elements, and has been certified gold by the RIAA for over 1 million units sold in the US. Sam Brown's self-titled debut Stop!, released in 1988, features the "Stop!", a soul-rock track that initially charted at number 52 on the before re-release propelled it to number four, with the reaching number 29 on the and appearing in year-end top Dutch albums at position 34. The sold over 100,000 copies in the UK, earning , driven by Brown's powerful vocals and Pete Wingfield's production emphasizing themes of emotional boundaries. The Spice Girls' "Stop", released in 1998 from their Spiceworld album, is a Motown-inspired pop track peaking at number three on the UK Singles Chart and number 16 on the Billboard Hot 100, marking their sixth consecutive US top-20 hit; it achieved platinum certification in the UK for over 600,000 sales. Lyrics focus on pausing rushed romance, accompanied by a music video homage to 1960s girl groups, and the song has amassed over 100 million Spotify streams as of 2023. Jane's Addiction's "Stop!", from their 1988 album , is an track written by and , topping Billboard's Tracks chart upon its 1990 single release and exemplifying the band's fusion of , metal, and with themes of restraint amid chaos. Talking Heads' live album (1984), derived from Demme's concert film, peaked at number 15 on the and remained charted for over two years, certified by the RIAA for 1 million US sales, featuring reinterpreted hits like "Once in a Lifetime" in an extended band format.

Science and technology

Medicine and anatomy

In , a centric stop denotes the opposing cuspal-fossae contacts that maintain the occlusal vertical dimension at , preventing excessive closure and ensuring stable in dental restorations or prostheses.00175-7/fulltext) Similarly, an occlusal stop functions as a limit, often synonymous with an occlusal , to resist vertical forces and stabilize removable partial against undercuts or displacement. These features are integral to prosthetic design, as they distribute occlusal loads anatomically across teeth and edentulous ridges, reducing stress on periodontal structures. Stopcocks, particularly three-way variants, serve as valves in medical devices to regulate or halt fluid through intravascular catheters, enabling precise control during procedures like or . Constructed typically from or with a rotating , they feature three ports for alternating flow directions, minimizing risks and facilitating blood sampling without disconnection. Their anatomical relevance lies in interfacing with vascular access sites, where improper sealing can lead to hemorrhage or , as documented in clinical protocols emphasizing torque-limited to prevent leaks under physiological pressures up to 300 . Cardiac arrest constitutes the sudden stoppage of effective heart contraction, resulting in circulatory failure and requiring immediate or CPR for survival. , roughly 350,000 out-of-hospital incidents occur yearly, with survival rates below 10% absent bystander intervention. Underlying causes include or , where myocardial electrical activity ceases, halting ventricular output despite potential atrial function. In microvascular anatomy, stop-flow phenomena describe localized cessation of amid global hemodynamic instability, as observed in sepsis-induced . This heterogeneity manifests as arteriovenous shunting bypassing nutrient-deficient beds in organs like the intestines or liver, exacerbating tissue ; experimental models quantify stop-flow thresholds at reduced pressures below 20 mmHg. Surgical contexts employ temporary vascular —akin to controlled stop-flow—for , limiting ischemia to minutes via clamps on arteries like the during aneurysm repair.

Linguistics

In , stop consonants, also termed plosives, are produced by a complete obstruction of in the vocal tract, followed by an abrupt release that generates a burst of sound. This articulatory mechanism involves articulators such as the lips, tongue, or velum forming a , building subglottal behind it, and then separating to allow the pressure to escape. Common examples in the include the voiceless bilabial /p/ (as in English "pin"), voiceless alveolar /t/ (as in "tin"), and voiceless velar /k/ (as in "kin"), alongside their voiced counterparts /b/, /d/, and /g/. Acoustic analysis of stop consonants, often visualized in spectrograms, reveals characteristic patterns such as a period of silence during closure, a brief burst at release, and transitions into adjacent vowels. A key temporal measure is voice onset time (VOT), defined as the interval between the stop release and the onset of vocal fold vibration, which distinguishes voiceless stops (longer VOT, often positive due to ) from voiced ones (shorter or negative VOT). For instance, English /p/ typically exhibits a VOT of 50-80 milliseconds, contrasting with /b/'s near-zero or pre-voicing. These features appear universally across languages, with stops forming core elements of inventories; from the UCLA Phonological Inventory Database (UPSID), sampling 451 languages, indicate that all included languages possess at least one series of oral stops, underscoring their phonological primacy. In grammatical and orthographic contexts, "full stop" denotes the period (.) punctuation mark, employed primarily to signal the termination of a declarative sentence or clause. Its historical origins trace to ancient Greek systems devised by Aristophanes of Byzantium around the 2nd century BCE, who introduced the stigmḗ teleía—a raised point indicating a complete pause at a thought's end, evolving through medieval scripts into the modern baseline dot. Style guides like The Chicago Manual of Style (17th edition) specify its use for ending sentences, abbreviating terms (e.g., "U.S."), and in lists, while advising against superfluous periods in headings or captions unless forming full sentences. Empirical corpus analyses, such as those from phonological databases, further highlight stops' prevalence, with voiceless plosives like /p/, /t/, and /k/ ranking among the most attested segments globally, appearing in over 90% of sampled languages' inventories.

Optics and photography

In optical systems, the aperture stop refers to the physical aperture that limits the bundle of rays passing through the to the , thereby controlling the quantity of admitted and defining the entrance pupil's effective diameter. This stop determines the , calculated as the ratio of the to the diameter of the aperture stop (f/D), which inversely scales with light-gathering capacity since on the varies proportionally to 1/(f-number)^2. For instance, an f/2.8 aperture admits four times more light than an f/5.6 aperture, assuming identical focal lengths, as derived from the equation and étendue conservation in paraxial . Historically, early photographic lenses employed Waterhouse stops, consisting of interchangeable metal plates with precisely cut circular inserted into a slot behind the lens, invented by John Waterhouse in 1858 to enable selectable exposure control without altering lens elements. These were standard in 19th-century view cameras until largely supplanted in the early 20th century by diaphragms, which use overlapping thin blades to form a continuously adjustable polygonal approximating a circle, improving precision and reducing vignetting in multi-element lenses. Contributions from firms like advanced iris implementations in high-precision optics, integrating them into anastigmat designs for corrected aberrations across aperture ranges. The aperture stop's diameter directly influences depth of field, with larger apertures (lower f-numbers) yielding shallower focus by reducing the cone of rays from off-axis points, increasing the circle of confusion beyond acceptable limits; conversely, stopping down to f/8 or higher extends acceptable sharpness across greater object distances via the hyperfocal formula H = f^2 / (N c), where N is the f-number and c the circle of confusion diameter. Light-gathering efficiency scales with aperture area (π (D/2)^2), enabling shorter exposures for dim scenes, as empirically demonstrated in astrophotography where doubling aperture diameter quadruples collected photons per unit time, though gains diminish at extremes due to aberrations. However, small apertures introduce diffraction blurring, governed by the Rayleigh criterion, where the angular resolution limit θ ≈ 1.22 λ / D (λ being wavelength) causes Airy disk overlap, rendering systems diffraction-limited below f/8 for visible light in typical 35mm formats./University_Physics_III_-Optics_and_Modern_Physics(OpenStax)/04%3A_Diffraction/4.06%3A_Circular_Apertures_and_Resolution)

Law and enforcement

Individual stops and searches

In the United States, the legal framework for individual stops and searches of persons originated with the Supreme Court's decision in Terry v. Ohio, 392 U.S. 1 (1968), which authorized police to conduct brief investigatory stops based on reasonable suspicion of criminal activity short of probable cause for arrest, and limited frisks for weapons upon an articulable belief that the suspect is armed and dangerous. The Court emphasized evaluation under the totality of circumstances rather than an officer's mere hunch, balancing individual privacy against officer safety and public security in high-crime contexts. This doctrine enabled proactive policing strategies, such as pedestrian stops in urban areas prone to violence, where empirical data indicate that visible enforcement elevates perceived risks of detection and apprehension for potential offenders, thereby deterring crimes like gun possession and assaults. A prominent implementation occurred in , where the New York Police Department (NYPD) expanded stop-and-frisk practices under policies emphasizing high-crime precincts, peaking at approximately 685,000 stops in 2011. This intensity coincided with substantial crime reductions, including homicides dropping from 2,262 in 1990 to 335 by 2012, per NYPD records aligned with FBI . Analyses attribute part of this decline to deterrence effects, as intensified stops in targeted areas increased the certainty of , disrupting patterns of illegal gun carrying and violent retaliation that statistical models link to elevated offending risks in specific demographics and locales. Critics highlight low contraband recovery rates, with NYPD data showing weapons found in only about 1.2% of stops and guns in far fewer, alongside demographic patterns where and individuals comprised over 80% of those stopped, raising claims of . However, studies adjusting for precinct-level rates and suspect descriptions from / reports find that stop demographics mirror those of identified perpetrators, with no evidence of racial animus driving decisions after controlling for behavioral indicators and location-specific offending probabilities. A Academies of Sciences review of , including stop-and-frisk variants, concluded moderate evidence of short-term reductions—particularly for —outweighing implementation costs when focused on hotspots, though long-term effects require further randomized trials. Following the 2013 federal ruling in Floyd v. City of , which deemed NYPD practices unconstitutional due to indirect and insufficient documentation, stops plummeted over 90% by 2014 amid mandated reforms like body cameras and supervisory oversight. While overall crime continued declining initially, a marked uptick occurred in 2020, with murders rising to 468 from 319 the prior year per NYPD statistics, alongside surges in shootings, illustrating potential causal trade-offs where reduced proactive interventions correlate with diminished deterrence and restored opportunities for opportunistic violence in under-policed areas. This pattern underscores the tension between procedural constraints and empirical public safety gains from targeted, suspicion-based stops.

Vehicle and motion stopping devices

Vehicle and motion stopping devices encompass engineered apparatuses that impede or arrest the of vehicles or mechanical systems through controlled application of , impact absorption, or puncture mechanisms, adhering to principles of Newton's second law where decelerative F = ma opposes p = mv. These devices convert translational into , deformation, or other dissipated forms, with effectiveness quantified by energy absorption capacity and stopping distances derived from such as v^2 = u^2 + 2as, where friction coefficient \mu determines braking efficiency via F_f = \mu N. Historical iterations trace to ancient caltrops, evolving into modern tire-deflation strips and crash-rated barriers, deployed in enforcement, security, and industrial contexts to mitigate collisions or unauthorized movement. In , spike strips—tubular arrays of hollow steel barbs coated in rubber—puncture and deflate s during high-speed pursuits, reducing vehicle control without immediate explosion to allow controlled stops typically within 1-2 miles. Deployment success varies, with alternatives to pursuits like stationary spike use deemed low-risk by analyses, though officer fatalities from errant vehicles during placement reached 26 since 1996, prompting tactical refinements. Caltrops, tetrahedral iron spikes predating warfare around 300 BCE, served analogous roles by impaling hooves of or , scattering across paths to create probabilistic hazards that slowed advances without direct confrontation; their four-point ensures one prong orients upward regardless of . Modern variants persist in tactical denial, though less common due to . Bollards, rigid posts often crash-rated to standards like ASTM F2656 (e.g., M50 rating stopping a 15,000-pound at 50 mph within 3.5 meters), employ shallow foundations and high-yield to resist ramming impacts via and resistance, dissipating energy through plastic deformation. In , such fixed barriers contribute to crash reductions of 33-48% in analogous speed-control implementations, per federal evaluations, by channeling or halting errant and deterring incursions into pedestrian zones; post-2010s vehicle-ramming incidents spurred widespread adoption, with layered designs enhancing layered protection against evolving threats. Mechanical applications include calipers, where hydraulic pistons clamp pads against rotating rotors, generating frictional \tau = r F_f that opposes , converting to thermal via KE = \frac{1}{2} I \omega^2, with pad materials engineered for coefficients \mu \approx 0.3-0.5 to achieve stopping from 60 mph in under 200 feet under optimal conditions. Railway buffer stops, fixed at track ends, utilize jaws or hydraulic dampers to grip rails or absorb collisions, providing progressive deceleration that limits forces to below 45,000 daN per pair of elements, preventing by distributing impact over strokes up to several meters. Patents for deployable spike variants emerged in the late , such as retractable road strips from onward, building on earlier tire-puncture concepts without supplanting foundational physics.

Computing and algorithms

Halting and termination

In low-level languages such as x86, the HLT halts the , suspending execution until an external , , or reset occurs. This privileged , encoded as 0xF4 in , prevents further fetching and execution, entering a low-power state while maintaining synchronization. In operating system kernels, HLT is employed in idle loops to conserve energy when no processes require , allowing resumption via timer interrupts or events. The , formalized by in , concerns whether a universal exists to determine, for any and input, if it will eventually terminate (halt) or loop indefinitely. Turing demonstrated undecidability through a proof: assuming a halting oracle H exists leads to a contradictory that does the opposite of H's prediction on itself, revealing no such general decider can exist for Turing-complete systems. This establishes foundational limits in , implying that properties dependent on termination, such as equivalence checking, are also undecidable in full generality. No algorithmic solution exists for the , but practical approximations mitigate risks in and execution. Timeouts impose resource bounds, forcibly terminating computations after a fixed or count to approximate non-halting behavior, as seen in testing frameworks and sandboxes. In higher-level languages, explicit termination mechanisms include Python's sys.exit(), which raises a SystemExit exception to end the interpreter process with an optional integer status code (0 for success, non-zero for errors), bypassing normal cleanup only if unhandled. Error handling constructs, such as try-except blocks leading to sys.exit() on failures, ensure controlled stops rather than crashes. Heuristics for detection provide partial solutions without resolving undecidability. Runtime monitors like EndWatch use lightweight tracing to identify non-termination, achieving 87% accuracy on standard benchmarks by detecting anomalies in execution patterns. Similarly, employs dynamic analysis to flag loops in real-world code, successfully identifying bugs like those in jEdit's editor. These tools rely on empirical patterns—such as repetition or resource exhaustion—validated through benchmarks in ACM proceedings, enabling proactive termination in debuggers and production environments while acknowledging theoretical incompleteness.

Other technical uses

Mechanical and general applications

In , limit stops, also known as endstops, are devices that halt the motion of machine components to prevent overtravel and potential damage. These typically consist of mechanical switches, sensors, or physical barriers that trigger upon reaching predefined positions, activating brakes or reversing motors. In elevators, ASME A17.1/CSSA B44 Safety Code mandates the use of automatic stop devices, such as switches on hoisting mechanisms, to cut power and engage brakes if the car exceeds safe terminal landing zones, ensuring compliance with minimum safety requirements for public installations. In additive manufacturing, limit stops serve a similar protective function in 3D printers by detecting the boundaries of movable axes, such as , and Z gantries, to avoid collisions and structural failures during homing or printing operations. endstops, often simple lever-actuated switches, provide reliable detection with precision up to ±0.01 , though optical or inductive variants offer alternatives for reduced wear in high-cycle environments. Stop valves, or shut-off valves, in systems function as mechanical controls to isolate flow in lines, allowing maintenance without disrupting broader supply networks. Corporation stops, installed at the connection between municipal mains and private lines, enable shutoff for line replacement while preserving main pressure; these or components adhere to standards post-1986 amendments, which banned lead content exceeding 8% in new pipes, , and fittings to mitigate health risks from . In applications, stop-loss mechanisms automate trade termination at predefined price thresholds to limit downside exposure, with backtests on strategies like trailing stops showing improved risk-adjusted returns over buy-and-hold in serially correlated markets, though tight thresholds can incur excessive costs. Empirical analyses, including Wilcoxon tests on historical , indicate stop-loss variants outperforming benchmarks in volatile conditions by capping losses, albeit with dependency on asset class and correlation structure.