A sign in sign language is a single word-like unit produced with the hands, body, and face. Just as spoken languages build words from individual sounds, sign languages build signs from a specific set of physical components: the shape of the hand, where it’s placed relative to the body, how it moves, which direction the palm faces, and what the face and head are doing. Change any one of those components and you can change the meaning entirely, the same way swapping a single sound in a spoken word (like “bat” to “cat”) creates a different word.
Signs are not mime or random gestures. They follow strict linguistic rules, belong to grammatical categories like nouns and verbs, and combine into sentences with their own syntax. There are over 149 documented sign languages worldwide, and linguists estimate the true number may exceed 400. Each one is a fully independent language with its own vocabulary and grammar.
The Five Building Blocks of a Sign
Linguist William Stokoe first described the internal structure of signs in the 1960s, identifying four core components. A fifth was added later by other researchers. Together, these five parameters are the smallest meaningful units in sign language, and every sign requires all of them.
- Handshape: The specific configuration of the fingers and thumb. ASL uses dozens of distinct handshapes. Using a flat palm versus a pointed index finger versus a fist will produce completely different signs.
- Location: Where the hand is positioned relative to the body. A sign made at the forehead means something different from the same handshape and movement made at the chin or chest.
- Movement: How the hand travels through space. This could be a tap, a circular motion, an arc, a wiggle of the fingers, or no movement at all.
- Palm orientation: The direction the palm faces. Palms facing up, down, inward, or outward can distinguish otherwise identical signs from one another.
- Non-manual markers: Facial expressions, head tilts, and body positioning that are produced simultaneously with the hand movements. These are not optional emotional flourishes; they carry grammatical meaning.
Why Facial Expressions Are Grammar
In spoken English, you change a statement into a question partly by raising your pitch at the end of a sentence. Sign languages accomplish similar things with the face and head. In ASL, lowering your eyebrows while signing is what marks a “wh-question” (who, what, where, when, why). Without that brow lowering, the same hand signs could read as a statement rather than a question.
Other non-manual markers include head shaking, tilting the head up or down, and leaning the body forward. Research on ASL grammar has shown that tilting the head down can signal a definite meaning (“the specific cat”), while tilting up may signal an indefinite one (“a cat” or “some cat”). The intensity of these signals also tracks with emphasis, similar to how you might stress a word in speech to highlight it. Without non-manual markers, the hand signs alone can only rarely form a comprehensible sentence in ASL.
Signs That Look Like What They Mean
One of the biggest differences between sign languages and spoken languages is iconicity: many signs visually resemble the thing they represent. The ASL sign for BANANA mimics peeling a banana. CANDLE depicts a flickering flame on top of a long thin object. HIPPO represents the animal’s wide mouth and four long teeth. The sign for TREE in ASL, Danish Sign Language, and Chinese Sign Language all represent the shape of a prototypical tree, even though these are separate, unrelated languages.
Spoken languages have a small version of this in onomatopoeia (“moo,” “ding-dong”), but sign languages use iconicity far more extensively. That said, signs are never pure pantomime. Even an iconic sign follows the formal rules of the language. The ASL sign for HEAR, for example, involves tapping the ear with an index finger. The ear location is iconic, but the choice of the index finger specifically, and the tapping motion rather than a rub or a flick, are arbitrary conventions that a learner has to memorize. A different sign language might represent “hear” in a completely different way, or the same concept might not be iconic at all.
How Signs Differ From Gestures
People sometimes assume sign language is an elaborate form of pantomime. Linguistically, signs and gestures are fundamentally different things. Signs have internal structure: they break down into smaller components (the five parameters above) that recombine to create new meanings, much like sounds combine to form words. Gestures are holistic. When you mime “drinking from a cup,” that gesture doesn’t decompose into reusable parts that show up in unrelated gestures.
Signs also belong to grammatical categories. A sign can function as a noun, a verb, or an adjective, and it behaves according to the grammatical rules of the language. Gestures don’t. When your brain produces a sign, it goes through the same type of word-selection and sound-retrieval process that spoken language uses. When it produces a gesture or pantomime, it relies on visual and motor imagery of the physical action instead.
Using Space as Part of the Language
Signs don’t just happen in front of the body. They use a three-dimensional signing space that extends roughly from the waist to the forehead. This space is not just a stage where signs are performed; it’s an active part of the grammar.
In ASL, spatial relationships between objects are expressed by placing handshapes in specific locations relative to each other. To describe a person standing to the left of a car, for instance, a signer places a V-shaped handshape (representing an upright person) to their left and a different handshape (representing a vehicle) to their right. The position, distance, and orientation of the hands directly map onto the position, distance, and orientation of the real-world objects. Even the tilt of the handshape matters: a classifier for a cup can be rotated to show the cup lying on its side. This system encodes a remarkable amount of spatial information simultaneously, something that spoken languages handle with strings of prepositions and descriptions.
How Signs Are Written Down
Sign languages don’t have a widely used writing system the way spoken languages do, but linguists and students use a convention called glossing to represent signs on paper. Glosses are written in ALL CAPITAL LETTERS to distinguish them from English words. A gloss like EAT represents the single ASL sign for “eat,” not the English word.
When a single sign requires multiple English words to translate, hyphens connect them: DON’T-LIKE or YOU-ASK-ME are each one sign. When two separate signs combine into a compound, a plus sign joins them: BOOK+STORE or EAT+NIGHT (meaning “dinner”). Fingerspelled words, where each letter is signed individually, appear with hyphens between letters (G-L-A-D-Y-S) or with a notation like (fs) before the word. Repetition of a sign is marked with plus signs: GIVE++ means the sign GIVE is repeated for emphasis or to indicate ongoing action.
Regional Variation and Signing “Accents”
Just like spoken languages have regional accents, sign languages have regional styles. Within ASL, signers on the West Coast tend to sign more slowly and with a more relaxed style, while East Coast signers typically sign faster. Some individual signs differ by region entirely. The sign for “slow,” for example, is produced differently depending on where the signer is from.
Variation also follows cultural and social lines. Black ASL, used primarily within African American Deaf communities, has its own distinct vocabulary and stylistic features that developed through decades of segregated Deaf schools. Age plays a role too: older signers may use signs that have fallen out of fashion with younger generations. Just as a spoken accent reflects where you grew up and who you grew up around, a signing style carries the same kind of social and geographic fingerprint.