What is language? How human language works

Language is a system of shared rules that lets people combine a small set of meaningless units, sounds in speech or handshapes in sign, into words, and words into an unlimited number of sentences that carry meaning. Every human community has one, and every healthy child learns one without being taught. What makes human language different from animal communication is not that it sends signals, but that it can say new things about anything, including what isn't there.

In short

• Language is built in two layers: meaningless sounds combine into words, and words combine into sentences, by rules every speaker knows without being able to state them.
• It can talk about the absent, the past, the future and the imaginary, and it can produce sentences no one has ever said before.
• There are a little over 7,000 living languages, sign languages among them, and every one is a full language, as complex as any other.

What counts as a language?

A language is more than a list of words. It is a set of rules, mostly unconscious, for how sounds may combine, how words are built, and how words are ordered to mean something. The US National Institute on Deafness and Other Communication Disorders puts it simply: "language is a set of shared rules" that allow people to express ideas in a meaningful way, while speech is talking, only one way to express it. Writing is another way, and a recent one: people spoke for tens of thousands of years before anyone wrote, as the note on cuneiform describes.

Sign languages are languages in exactly the same sense. American Sign Language, British Sign Language and the hundreds of others have their own grammars, unrelated to the spoken languages around them, and children learn them on the same schedule as speech. The clearest proof came from Nicaragua. When schools for deaf children opened in Managua in 1977 and 1980, children who had used only private home signs began to combine them, and within a few years a new language had formed. The younger children who learned it from the older ones added grammar the first group used less or not at all, such as using the space around the body to show who did what to whom, as the account of Nicaraguan Sign Language sets out.

What makes human language different from animal communication?

In 1960 the linguist Charles Hockett listed what he called the design features of language, 13 at first and later 16, as summarized in the overview of Hockett's design features. Many animals share some of them. Three, taken together, mark human language out.

• Displacement: talking about what is not here and now. "My grandmother grew up by the sea" refers to a person, a place and a time none of which is present.
• Productivity: making and understanding sentences never heard before. You have probably never read the sentence "a purple giraffe borrowed my bicycle," and you understood it at once.
• Duality of patterning: building meaning in two layers. Sounds that mean nothing on their own combine into words that do.

Here is how the three compare with the best-studied animal signals:

	Displacement	Productivity	Duality of patterning
Honeybee waggle dance	Partly: points the way to food out of sight	Only for direction and distance	No
Vervet monkey alarm calls	No: each call is for a predator that is present	No: a fixed set of calls, one for leopards, one for eagles, one for snakes	No
Human language	Yes: anything, anywhere, at any time, real or imagined	Yes: no limit to new sentences	Yes: about 40 sounds make tens of thousands of words

No animal system studied so far has all three, and none combines units into new messages with rules the way a human child does by age three.

How does a handful of sounds make unlimited meaning?

Take duality of patterning step by step.

1. English has about 40 distinctive sounds, depending on the accent. A sound on its own, such as the "k" at the start of cat, means nothing.
2. Combine three of them, /k/, /æ/ and /t/, and you get cat. Rearranged, the same three sounds give act and tack: three different meanings from one set of meaningless pieces.
3. Words combine into sentences by rules of order. "The dog bit the man" and "The man bit the dog" use exactly the same words and mean opposite things.
4. Sentences can be put inside sentences: "The man said that the dog that bit him was his neighbor's." There is no longest sentence, because one more clause can always be added.

So a speaker with a vocabulary of a few tens of thousands of words can produce more sentences than anyone could say in a lifetime. To write those sounds down unambiguously, linguists use the International Phonetic Alphabet, one symbol for each sound, which is how /k/ and /æ/ are written above.

How many languages are there?

Ethnologue, the most widely used catalog, lists a little over 7,000 living languages in its 2025 edition, counting those still used by at least one person as a first language, according to Our World in Data. The exact number is uncertain, for two reasons. Many languages are still poorly documented. And there is no linguistic test that separates a language from a dialect: speakers of Danish, Norwegian and Swedish can often understand each other, yet they count as three languages, while some forms of Chinese that are not mutually understandable are often called dialects of one. Politics, history and identity draw many of those lines.

Languages also die. Most of the world's languages have few speakers, and when children stop learning one, it can vanish within a few generations. Languages are related to each other in families, descended from common ancestors the way English and Hindi both descend from one ancient language, as the note on language families explains.

How do children learn language?

Without lessons. Babies begin babbling speech-like sounds at around 4 to 6 months and usually have one or two words by their first birthday, according to the NIDCD; within a few more years they use complex sentences. Children are not mainly imitating. A child who says "I goed" or "two mouses" has never heard those forms; they have worked out a rule, add -ed for the past, and applied it too widely. That is productivity at work.

There seems to be a window for learning a first language. The NIDCD notes that there appear to be critical periods for speech and language development in young children, and children who hear or see no language in early life struggle to learn one fully later. How much of this ability is built into the human brain, and how much comes from general learning, is one of the oldest arguments in linguistics; the note on how the brain works covers the regions involved.

Does the language you speak shape how you think?

This is the question known as the Sapir–Whorf hypothesis, after the linguists Edward Sapir and Benjamin Lee Whorf, though neither stated it as one hypothesis. It comes in a strong and a weak form.

Still argued

The strong form, linguistic determinism, says language sets the limits of thought, so speakers of a language without a word for something can't think it. Contemporary linguists have largely abandoned it, as the overview of linguistic relativity notes; Whorf's famous claim that the Hopi language had no way to speak of time as units was challenged in 1983 by Ekkehart Malotki, who documented Hopi words and calendars for exactly that. The weak form says language nudges attention and memory without limiting them, and it has real experimental support. In a 2007 study, Russian speakers, whose language requires separate words for light blue and dark blue, were faster at telling two blues apart when the colors fell on opposite sides of that line; English speakers showed no such edge, and the effect vanished when a word task occupied the Russians. Researchers still argue over how large and how general such effects are.

The best-known example in this debate is a myth. The claim that Eskimo languages have dozens or hundreds of words for snow grew from the work of the anthropologist Franz Boas, who gave no such number, and later writers inflated it until a New York Times editorial in 1984 put it at 100, as the history of the claim records. Inuit and Yupik languages build long words from roots and suffixes, so any count depends on what a "word" is. Fieldwork by the anthropologist Igor Krupnik and others has since found that some of these dialects do have far more terms for snow and ice than English, 40 or 50 or more, as people who live with snow would need; English, too, has slush, sleet, powder, drift and flurry. Having words for what matters to you is a fact about vocabulary, not proof that language limits thought.

Where does language lead next?

Language underlies almost everything else people do with words: writing, which began as a way of recording speech, as told in the history of the alphabet; persuasion, studied as rhetoric; and now machines that model it, such as large language models, which learn statistical patterns from vast amounts of text. Whether such systems have language in Hockett's full sense, or only its surface, is a question the features above help to ask clearly.

Check yourself

• Without looking back: name the three design features that set human language apart, with an example of each.
• Why does a child saying "I goed" show that language is more than imitation?
• What is the difference between the strong and weak forms of the Sapir–Whorf hypothesis, and which has evidence behind it?

Sources

• Speech and Language Developmental Milestones — National Institute on Deafness and Other Communication Disorders, 2022
• Russian blues reveal effects of language on color discrimination — Winawer and colleagues, PNAS, 2007
• Number of living languages — Our World in Data, from Ethnologue, 2025
• Hockett's design features — Wikipedia
• Linguistic relativity — Wikipedia
• Eskimo words for snow — Wikipedia