Glossary

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Languaging

A sociolinguistic concept that reframes language as an ongoing activity rather than a fixed system. Developed by scholars including Alastair Pennycook and Li Wei, languaging treats communication as the dynamic use of all available linguistic and semiotic resources — words,…

Langue des Signes Québécoise(also: LSQ, Quebec Sign Language)

The sign language used by the Deaf community in francophone Quebec and in francophone Deaf communities elsewhere in Canada. LSQ is a distinct natural language with its own grammar, lexicon, and cultural tradition — not a signed version of French — and developed historically from…

Lexical NMS(also: Lexical Non-Manual Sign)

Non-manual signs that are an integral part of a specific sign's production, required to distinguish it from other signs that share the same manual component. For example, the ASL sign for "NOT YET" includes a hand gesture combined with the tongue touching the lower lip and a…

Libras(also: Brazilian Sign Language, Língua Brasileira de Sinais)

The official sign language of the Deaf community in Brazil, recognized by Brazilian federal law (Law No. 10.436/2002) as a legitimate means of communication and expression. Libras has its own grammar, syntax, and linguistic structure distinct from spoken Brazilian Portuguese. It…

Low-Resource Sign Language

A sign language for which standardised corpora, training data, technical infrastructure, and institutional support are limited compared to 'high-resource' sign languages like American Sign Language (ASL) or German Sign Language (DGS). Low-resource sign languages — such as Bangla…

MPEG-4 Facial Action Parameter(also: MPEG-4 FAP, FAP, Facial Action Parameter)

A standard for 3D face animation defined in ISO/IEC 14496-2 (MPEG-4), which parameterises a face through 68 feature points whose displacements (scaled relative to the character's own facial proportions) encode any facial expression. MPEG-4 FAP is proportion-invariant, so the…

Makaton

A language programme that uses a combination of speech, signs (borrowed from British Sign Language), and graphic symbols to support communication for people who have difficulty with spoken language. Unlike BSL, which is a complete natural language with its own grammar, Makaton…

Manual Sign(also: MS, Hand Sign)

The hand shapes, movements, and locations that form the primary visible component of sign language vocabulary. Manual signs are what most hearing people think of as "sign language," but they represent only one channel of a multi-channel visual communication system. In ASL,…

Manual Signs(also: Hand Signs)

The hand-based components of sign language communication, consisting of four parameters: hand shape (configuration of fingers), location (where the sign is made relative to the body), movement (how the hands move through space), and palm orientation. Manual signs form the core…

Milan Congress(also: Milan Congress of 1880, Second International Congress on Education of the Deaf)

The Milan Congress was an international conference on the education of Deaf children held in Milan in 1880, where hearing educators voted to ban sign language from Deaf schools and impose oralism, the exclusive use of speech and lip-reading, as the standard pedagogy. The…

Morphological NMS(also: Morphological Non-Manual Sign)

Non-manual signs that modify or add grammatical meaning to manual signs, functioning similarly to morphemes in spoken languages. In ASL, morphological NMS convey information about degree, intensity, size, and manner. For example, facial expressions and body posture can show…

Multichannel Signal(also: Multi-Channel Signal, Parallel Signal Channels)

A communication signal that conveys information simultaneously through multiple independent or semi-independent channels. In the context of sign languages, a multichannel signal includes the concurrent streams produced by a signer: manual signs (dominant and non-dominant hand…

Native Signer(also: Native Sign Language User, L1 Signer)

A person who acquired a sign language as their first language (L1) during the critical period of language development, typically before age 5. Native signers usually learned sign language from deaf parents or through early immersion in deaf education environments. In…

Non-Manual Features(also: NMF, Non-Manual Markers, Non-Manual Signals)

The facial expressions, mouth movements, eye gaze, head tilts, and body postures that convey grammatical and semantic information in sign languages, functioning alongside manual hand signs. Non-manual features can indicate questions (raised eyebrows), negation (head shake),…

Non-Manual Markers(also: NMMs, Non-Manual Signals, Facial Grammar)

Grammatical elements in sign languages conveyed through facial expressions, head movements, eye gaze, and body posture rather than hand movements. In American Sign Language, non-manual markers are essential for conveying grammatical information such as questions (raised eyebrows…

Non-Manual Markers(also: Non-Manual Signals, NMMs, Facial Grammar)

Facial expressions, head movements, eye gaze, mouth movements, and body postures that convey grammatical information in sign languages. Unlike facial expressions in spoken languages which primarily convey emotion, non-manual markers in sign languages serve linguistic functions:…

Non-Manual Sign(also: NMS, Non-Manual Marker, Non-Manual Signal)

Facial expressions, head movements, eye gaze, mouth movements, and body posture that serve essential grammatical and linguistic functions in sign languages. In ASL, NMS perform lexical functions (distinguishing between signs like CLEAN and VERY CLEAN), morphological functions…

Non-Manual Signal(also: NMS, Non-Manual Marker, NMM)

A linguistic component of sign languages that is expressed through parts of the body other than the hands, including facial expressions, eyebrow movement, head tilts, shoulder shifts, mouth movements, and eye gaze direction. Non-manual signals serve critical grammatical…

Non-Manual Signals(also: Non-Manual Markers, NMS, NMM)

Linguistic information conveyed through parts of the body other than the hands in sign languages, including facial expressions, mouth movements, eye gaze, head tilts, head shakes, and body shifts. In American Sign Language and other sign languages, non-manual signals serve…

Non-Manual Signs(also: Non-Manual Markers, NMS, NMM)

Components of sign language that are produced without the hands, including facial expressions, mouth movements, eye gaze direction, head tilts, body posture, and shoulder shifts. Non-manual signs are not merely expressive additions but are grammatically essential in sign…

Non-manual markers(also: NMM, Non-manual signals, Facial grammar)

Linguistic features in sign languages that are conveyed through facial expressions, head tilts, eye gaze direction, mouth movements, and body posture rather than through hand signs. Non-manual markers serve grammatical functions in ASL and other sign languages — including…

OpenPose

An open-source computer vision library developed by Carnegie Mellon University that detects human body, hand, facial, and foot keypoints in real-time from images or video. OpenPose extracts 25 body keypoints, 21 keypoints per hand, and 70 facial landmarks, providing a skeletal…

Phonology(also: Sign Language Phonology)

The study of the smallest meaningful units that make up language and the rules governing their combination. In sign languages, phonology describes the building blocks of signs: handshape, location on the body, movement, palm orientation, and non-manual signals. William Stokes…

Picture-in-Picture(also: PiP, PIP)

A display technique that shows a smaller video or content window overlaid on the main content, allowing viewers to see two sources simultaneously. In accessibility contexts, picture-in-picture is the primary method for presenting sign language interpretation in video and…

Pidgin Signed English(also: PSE, Contact Signing, Sign Supported English)

A hybrid communication system that combines elements of American Sign Language (ASL) and English. In PSE, signers use ASL signs for the main content words of an English sentence, following English word order, but generally do not include extra signs for English word endings or…

Polar Motion Profile(also: PMP)

A Polar Motion Profile (PMP) is a computational technique used in sign language detection that models the quantity and distribution of motion relative to a detected face using polar coordinates. The method captures the characteristic hand and arm movements associated with…

Pose Estimation(also: Body Pose Estimation, Skeleton Tracking)

A computer vision technique that detects and tracks the positions of human body joints, hands, and facial landmarks from images or video. In accessibility contexts, pose estimation is a foundational technology for sign language recognition systems, gesture-based interfaces, and…

Prosodic Breaks(also: Prosodic Pauses, Prosodic Boundaries)

Pauses or breaks in the flow of communication that convey grammatical, syntactic, or emphatic meaning. In sign language, prosodic breaks occur between signs and serve functions similar to intonation and pausing in spoken language — marking sentence boundaries, separating clauses…

Referential Drift

Referential drift is a failure mode in AI-generated sign language where spatial loci — the established positions in signing space used to refer to people, objects, or locations — shift or are not maintained consistently across a sentence. Because signed languages use spatial…

Regional Sign Variation(also: Sign Language Dialect, Regional Sign Dialect)

Regional sign variation refers to systematic differences in the form of signs across geographic regions within a single sign language, analogous to dialects in spoken languages. Variation arises from local Deaf school traditions, contact between communities, and historical…

Reverse Dictionary(also: Sign-to-English Dictionary, ASL-to-English Dictionary)

A dictionary tool that allows users to search for the meaning of a sign language sign by inputting its visual or linguistic properties — such as handshape, location, movement, and orientation — rather than searching from a known English word. Reverse dictionaries address the…

Search-by-Feature(also: Feature-based sign search, Linguistic-property search)

A sign-language dictionary search technique in which a user manually selects linguistic properties of the target sign — typically handshape, body-relative location, movement type, orientation, and number of hands — from a menu, and the system returns dictionary entries matching…

Search-by-Video(also: Video-based search, Search by video)

A sign-language dictionary search technique in which a user performs a sign into a webcam or camera and computer-vision-based sign recognition returns a ranked list of candidate dictionary entries. Search-by-video is easier for novice signers than search-by-feature because it…

Sign Duration(also: Sign Speed, Signing Speed)

The average time spent performing individual signs during sign language production, typically measured in seconds. Sign duration is a key parameter in sign language animation that affects both understandability and user satisfaction. Research has shown that DHH users of ASL…

Sign Language Classifier(also: Classifier Sign, Depicting Sign, Classifier Predicate)

A type of sign in sign languages that is not part of a fixed vocabulary but is created dynamically during discourse to represent a class of objects sharing a common shape, size, or physical characteristic. Classifiers function as "super-pronouns" — they replace and describe…

Sign Language Dictionary(also: SL Dictionary, ASL Dictionary)

A reference tool that allows users to look up signs in a sign language, providing video demonstrations, definitions, and usage examples. Sign language dictionaries can be organized by English gloss (word-based lookup), linguistic features (handshape, location, movement), or…

Sign Language Generation(also: Sign Language Synthesis, Signing Generation)

The automatic production of sign language content, typically through computer-generated animations of signing avatars or video synthesis. Sign language generation systems convert text or symbolic representations of signs into visual output, often using motion-capture data,…

Sign Language Interface(also: Sign-language interface, Signing interface)

A computing interface that accepts input from, or presents output to, a user in a signed language such as American Sign Language (ASL) or British Sign Language (BSL), rather than assuming a spoken or written language. Sign-language interfaces span sign-language recognition…

Sign Language Interpretation(also: Sign Language Interpreting, SLI)

The process of conveying spoken or written language into a sign language (or vice versa) by a trained interpreter, enabling communication access for Deaf and hard of hearing individuals. In digital media and immersive environments, sign language interpretation is typically…

Sign Language Learning(also: Sign Language Education, Sign Language Acquisition)

The process by which people learn a sign language as a first or second language, through instruction, immersion, or self-directed study. For hearing second-language learners, reading back fingerspelling and comprehending fast, connected signing are reported as the hardest skills…

Sign Language Phonology

The study of the smallest meaningful units that make up signs in signed languages, analogous to phonemes in spoken languages. In American Sign Language, signs are composed of phonological parameters including handshape, movement, location (place of articulation), and non-manual…

Sign Language Synthesis(also: Sign Language Generation, Sign Language Avatar, Signing Avatar)

Sign language synthesis is the automated generation of sign language output, typically through 3D animated avatars or computer graphics, from text or other input. The technology involves translating written or spoken language into the grammar, vocabulary, and spatial expressions…

Sign Language Writing System(also: Sign Language Script, Sign Language Notation, Sign Language Character System)

A system of symbols or characters designed to represent sign language in written form. Unlike spoken languages, which have well-established writing systems, sign languages generally lack a standard written form — meaning the approximately 70 million people worldwide who use sign…

Sign Linguistics(also: Sign Language Linguistics)

The scientific study of the structure and properties of sign languages. Sign linguistics examines the phonological, morphological, syntactic, and semantic components of visual-gestural languages. Key parameters studied include handshape (approximately 90 distinct configurations…

Sign Name(also: ASL name sign, Name sign)

A unique sign in American Sign Language (or another signed language) used to uniquely identify an individual person or, in some proposals, an object or device, in place of fingerspelling their English name. Sign names are culturally significant in Deaf communities and are…

Sign Phoneme(also: cheremes, sign language phoneme)

The smallest contrastive units in sign language that bear meaning and distinguish one sign from another, analogous to phonemes in spoken language. Sign phonemes include hand shapes, movements, locations, and orientations that combine to form signs. In sign language recognition…

Sign Spotting(also: Sign Detection, Continuous Sign Spotting)

Sign spotting is the task of automatically locating instances of specific signs within a continuous signing video, as opposed to classifying a pre-segmented isolated sign. It is a building block for search-by-sign in archive footage, automatic captioning of signed media, and…

Sign Vocabulary(also: Signing Vocabulary, Sign Lexicon)

The set of signs that a person knows or that a sign language recognition system can identify. In the context of sign language technology, vocabulary size is a critical constraint that determines a system's practical utility — current AI-powered sign language recognition systems…

Sign Writing(also: SignWriting, Sutton SignWriting)

A graphical notation system for writing sign languages, developed by Valerie Sutton in 1974. Sign Writing uses visual symbols to represent hand shapes, movements, facial expressions, and body positions used in signing, enabling sign languages to be written and read in a visual…

SignWriting

A writing system for sign languages that uses visual symbols to represent handshapes, movements, facial expressions, and body positions. Created by Valerie Sutton in 1974, SignWriting allows sign languages to be written and read without translation into a spoken language. Unlike…