Every day, billions of people turn a silent thought into sound waves or written symbols that another mind can understand almost perfectly. This everyday miracle is called language.
Despite being central to human life, language is surprisingly hard to define. This guide explains what language is, what makes it special, how it is built, how children learn it, and why it matters. Each fact that can be checked is explained with its source at the end.
Every day, billions of people turn a silent thought into sound, signs or written marks that another mind can understand. We do this so easily that we rarely stop to ask how it works. Linguists, the scientists who study language, still do not all agree on one definition of language. But they agree on many important features, and this guide covers those.
It explains the working definition, the design features that set human language apart, five levels of language, speech, writing and sign, how children learn language, how languages vary and change, and common myths. It ends with worked examples, a glossary, a list of sources and ten practice questions.
At its simplest, language is a structured system of communication that uses symbols, such as sounds, gestures or written marks, combined according to rules, to carry meaning. This definition has three essential parts:
The word "rain" is a symbol. The rule that lets us say "it is raining" but not "raining it is" is structure. The shared understanding that speaker and listener are both thinking of water falling from clouds is meaning. Language exists where all three meet.
Human societies have produced a very large number of languages. The research organisation Ethnologue lists about 7,160 living languages today. The exact number changes, and different catalogues give different totals, partly because there is no sharp line between a language and a dialect. So you will see figures such as "about 7,000" in different books.
Ethnologue also reports that roughly 40% of the world's languages are endangered, often with fewer than 1,000 users remaining. At the same time, just 23 languages are used by more than half of the world's people. This means that a small number of languages have huge numbers of speakers, while thousands have very few. These figures are updated regularly, so check the source for the latest numbers.
Many animals communicate. Birds sing, bees dance and many mammals call to each other. Scientists have long asked what, if anything, separates human language from these systems. In 1960 the American linguist Charles Hockett published a list of design features of human language in an article called "The Origin of Speech". He first listed 13 features and later added more, to reach 16. Linguists still use several of them to compare communication systems, although the list has been revised and criticised, for example because it was based mainly on spoken language.
Here are the features that textbooks usually treat as most important.
| Feature | What it means | Example |
|---|---|---|
| Arbitrariness | Most words have no natural link to what they mean | "Dog" in English, "chien" in French, "perro" in Spanish |
| Productivity | Speakers can make and understand new messages that no one has said before | "The purple elephant read my homework" is new, but you understand it |
| Displacement | We can talk about things that are not here and now | Last year's holiday, tomorrow's exam, or an idea like "justice" |
| Duality of patterning | A small set of meaningless sounds combines to make many meaningful words | The sounds p, i and t make "pit" and "tip". The sounds alone mean nothing |
| Discreteness | Language is built from separate units | "Bin" and "pin" differ by one sound and mean different things |
| Cultural transmission | People learn their language from others around them | A child learns the language spoken at home |
| Reflexiveness | We can use language to talk about language | "What does 'arbitrary' mean?" |
Productivity is worth a closer look. A finite set of words and rules can produce a number of sentences that is, in principle, unlimited. Because of this, you can understand a sentence you have never heard before.
The best-known example is the honeybee. The Austrian scientist Karl von Frisch showed, through experiments over many years, that a bee which finds food can tell the other bees in the hive the direction and distance of it, by moving in a pattern called a dance. For this work he shared the 1973 Nobel Prize in Physiology or Medicine. According to the Nobel Prize announcement, a bee that finds food near the hive does a "round dance", and when the food is further away, it does a "waggle dance" along a straight line, whose direction and length carry the information.
The bee dance has displacement, because it describes a place that the bees are not at now. But it is limited to a few kinds of information, such as the position of food or a new nest site, so its productivity is limited. Other animal systems are also studied. Researchers have tried to teach signs or symbols to apes, and the results are still debated. This article does not claim that animals cannot communicate well. Its point is narrower: human language has a combination of features that no other known system has in full.
Diagram 1. Three systems compared on three design features. "Limited" means the feature exists in a narrow form.
Linguists study language at five connected levels. Each level studies a different part of how communication works.
| Level | What it studies | Example |
|---|---|---|
| Phonology | The sounds of a language and the rules for combining them | "Blick" could be an English word, but "bnick" could not, because English does not begin words with "bn" |
| Morphology | How words are built from smaller meaningful parts | "Unhappiness" = un- (not) + happy + -ness (state) |
| Syntax | How words combine into sentences | "The cat sat on the mat" is correct. "Mat the on sat cat the" is not |
| Semantics | The meaning of words and sentences | "Bank" can mean the side of a river or a place for money |
| Pragmatics | How context shapes meaning | "Can you pass the salt?" is a request, not a question about ability |
Diagram 2. The five levels of language, shown with the sentence "Could you reopen the windows?"
Many people think writing is the "real" language. Linguists see it the other way round. Speech is the main form of language, and it is much older. Scholars do not agree exactly when human language began. But the earliest known writing appeared only about 5,000 years ago, around 3300 to 3000 BCE, in Sumer, in what is now southern Iraq, and Egyptian writing appeared at about the same time. Many languages today are mainly spoken and have no standard written form, yet they are fully developed languages.
| Type of writing system | How it works | Examples |
|---|---|---|
| Alphabet | Symbols stand for consonants and vowels | English, Greek, Russian |
| Abjad | Symbols mainly stand for consonants | Arabic, Hebrew (Urdu is written with a script based on Arabic) |
| Abugida | Each symbol is a consonant with a built-in vowel | Hindi in the Devanagari script |
| Syllabary | Each symbol stands for a syllable | Japanese kana |
| Logographic | Symbols mainly stand for words or ideas | Chinese characters |
Sign languages are full languages too. Before the 1960s, many people thought that American Sign Language (ASL) was only a collection of gestures. In 1960 William Stokoe published Sign Language Structure, the first modern linguistic study of ASL, with support from the US National Science Foundation. He showed that ASL has its own structure, and later research confirmed that it has its own grammar. The National Science Foundation now describes ASL as a fully formed language with its own syntax and morphology. Sign languages differ around the world. They are not signed versions of the spoken languages around them.
Children everywhere learn the language of the people around them, usually without formal lessons. The US National Institute on Deafness and Other Communication Disorders (NIDCD) says that the most intensive period for speech and language development is the first three years of life. Typical steps look like this, but children vary a lot.
| Age (typical) | What often happens |
|---|---|
| Birth to 3 months | Cooing and pleasure sounds |
| 4 to 6 months | Babbling in a speech-like way |
| By about 1 year | One or two simple words |
| By about 2 years | Putting two words together, such as "more milk" |
| Around 3 to 5 years | Longer sentences and a growing vocabulary |
Children do not only copy. They often say forms such as "goed" or "mouses", which they have never heard an adult say. This suggests that they are noticing patterns and applying rules, then gradually learning the exceptions. If you are worried about a child's speech or hearing, a doctor or a speech-language pathologist can advise.
No language is a single, fixed thing. Within one language, people speak in different accents (ways of pronouncing) and dialects (differences in vocabulary and grammar too). Linguists find that every dialect follows its own regular rules. Languages also change over time, and they borrow words from each other. English has borrowed from many languages, including those of South Asia.
| English word | Comes from |
|---|---|
| pyjamas | Hindi and Urdu (pāy-jāma) |
| shampoo | Hindi (chāmpo) |
| jungle | Hindi (jangal) |
| bungalow | Hindi (banglā) |
| algebra | Arabic (al-jabr) |
| chocolate | Nahuatl, through Spanish |
You can read more about how English spread and borrowed in English as an International Language.
Language is closely tied to who people are. It carries a community's stories, humour and customs, and many communities work to keep their languages alive. Researchers also ask how far the language you speak shapes the way you think. This idea is called linguistic relativity, and scientists still debate how strong the effect is. Most researchers agree that thought is not simply limited by language, and some studies report small effects of language on how people notice or describe things.
Language depends on the brain. Damage to the parts of the brain responsible for language, for example after a stroke, can cause aphasia, a condition in which a person has difficulty speaking, understanding, reading or writing. Speech-language pathologists help people recover as much as they can. These conditions show that language is a special skill supported by specific brain systems, and not only a habit learned from others.
Understanding the levels of language helps explain technology such as voice assistants. To follow "Can you set an alarm for seven tomorrow?", a system must recognise the sounds (phonology), work out the word order (syntax), decide that "seven" means a time (semantics) and treat the sentence as a request (pragmatics). Computers handle these tasks with methods very different from those of the human brain, and whether this counts as "understanding" is still debated.
Take the sentence: "Could you reopen the windows?"
Try it yourself: analyse "Unhappy students cannot concentrate." at the morphology and syntax levels. Sample answer: Morphology: un- + happy, student + -s, and can + not. Syntax: the subject "unhappy students" comes first, then the verb group "cannot concentrate".
The colours are arbitrary, because red means "stop" only by convention. But a system needs more than one feature to count as a full language. A traffic light is a useful code, but not a language.
Try it yourself: is Morse code a language? Sample answer: No. Morse code is a way of writing the letters of an existing language with dots and dashes. It can carry any message, but only because it stands for letters of a language such as English.
Language is not simply a tool that humans use. It is part of how we think, learn and belong to a community. Understanding what language is shapes how teachers teach reading and writing, how speech therapists help people recover after brain injury, how computer scientists build translation and voice software, and how societies think about identity, culture and belonging. The next article in this series, Language and Its Need, explores why humans need language so much.
Activity: ask students to choose a communication system, such as a traffic light, a flag or a bee dance, and test it against the three design features in Diagram 1. Then ask them to say what it would need before it counted as a full language.
Please note: examples are original, written for teaching. Figures such as the number of languages change as research continues, so check the sources below for the latest numbers. Scientists still debate several points in this article, and where they do, the article says so.
10 questions. Select an answer for each, then submit to see your score instantly.