In 1871 Lewis Carroll published a poem that begins: "'Twas brillig, and the slithy toves / Did gyre and gimble in the wabe." Almost none of these words exist, yet any English speaker knows toves are things, probably several. Slithy describes them. Gyre and gimble are things they did. The poem shows that grammar carries information on its own, separate from the meanings of words. This level looks at how words are built and how sentences are put together.

The parts of words

A word like "unhappiness" has three parts: un, happi and ness. A morpheme is the smallest unit of language that carries meaning. Some morphemes, like happy, can stand alone; others, like un and ness, must attach to something. Linguists call this field morphology.

Morphemes do two main jobs. Inflection changes a word's grammatical form without making a new word, as when walk becomes walked or cat becomes cats. Derivation creates a new word, often of a new type, as when happy becomes happiness or teach becomes teacher. English also makes words by compounding (smartphone) and blending (brunch).

Different ways to build words

Languages differ greatly in how much they pack into a word. Isolating languages, such as Mandarin and Vietnamese, use mostly one-morpheme words, relying on word order and separate small words to show grammar. Agglutinative languages, such as Turkish, stack many clear-cut suffixes onto a root. The Turkish word evlerimizden means "from our houses": ev (house), ler (plural), imiz (our), den (from). Polysynthetic languages, such as Mohawk and Inuktitut, can pack the meaning of a whole English sentence into one word.

These types are tendencies, and most languages mix them. Nineteenth century scholars sometimes ranked them, but no type is more primitive. English itself has moved over a thousand years from the heavy word endings of Old English toward a more isolating style.

Word order

Sentences have parts that play roles: a subject, a verb and often an object. Languages favor different basic orders. English, Mandarin and Swahili usually put subject, then verb, then object (SVO): "The child eats rice." Japanese, Turkish and Hindi usually put the verb last (SOV). Welsh, Irish and Classical Arabic often put the verb first (VSO). The most common basic orders among the world's languages are subject, object, verb and subject, verb, object, and together they cover most languages surveyed. Languages that mark roles with word endings, as Latin and Russian do, can allow much freer order, because the endings show who did what to whom.

In 1963 the American linguist Joseph Greenberg found patterns that hold across many unrelated languages. One is that languages that put the verb before the object tend to use prepositions, while languages that put the object first tend to use postpositions. English says "to Tokyo," while Japanese says the equivalent of "Tokyo to."

Structure, not strings

A sentence is not a row of beads. Sentences are built from nested phrases, called constituents, not just strings of words. In "The tall woman left early," the words "the tall woman" form a unit: you can replace them with "she," but you cannot replace "woman left" with any single word.

Structure explains ambiguity. "I saw the man with the telescope" can mean you used a telescope, or that the man had one. The words are identical; what differs is how they group. In one reading "with the telescope" attaches to "saw"; in the other it attaches to "the man."

Structure also allows recursion. Recursion lets a phrase contain another phrase of the same type, in principle without limit. An old nursery rhyme shows it: "This is the rat that ate the malt that lay in the house that Jack built." Each "that" clause sits inside the one before. Many linguists have treated recursion as a core feature of all languages. The American linguist Daniel Everett argued in 2005 that Pirahã, spoken in the Brazilian Amazon, lacks it, and other linguists disputed his analysis. The debate remains open, partly because very few outsiders speak Pirahã.

Worked example: headlines that mean two things

Newspaper headlines drop small words to save space, and the result sometimes shows grammar at work. Consider a classic: "Squad Helps Dog Bite Victim."

The intended reading groups "dog bite victim" together as one noun phrase: a person who was bitten by a dog, whom the squad helped. The comic reading groups the words differently: "helps" takes "dog" as its object, and "bite victim" becomes what the dog is helped to do. Same words, same order, two structures. A reader who chuckles has just parsed the sentence twice.

Now take "Old men and women were evacuated." Does "old" describe only the men, or the men and the women? In one structure, "old men" is a unit joined to "women." In the other, "old" applies to the whole phrase "men and women." Writers fix this by adding words: "women and old men," or "old men and old women."

In both cases speakers sort out the meaning so quickly that they rarely notice they are choosing between structures. That speed is a sign of how much grammar every native speaker carries without being taught.