What Are Brown's 14 Morphemes?
Brown's 14 morphemes are the grammatical inflections and function words that mark the beginning of true syntactic development in English-speaking children. They include three prepositions, three present-tense verb inflections, two past-tense forms, four forms of *be*, the regular plural -s, the possessive -'s, and articles.
Why they matter. A child can produce many words without producing any of these morphemes — telegraphic speech ("baby eat cookie") is built entirely from content words. Once a child starts adding morphemes ("baby is eating the cookie"), they have moved out of telegraphic speech and into productive grammar. Tracking which morphemes have emerged is the most direct way to measure where in early grammatical development a child sits.
The stable order. Brown (1973) showed that the order of acquisition is remarkably stable across children, even though the *age* at which each morpheme is mastered varies. Present progressive -ing comes first; the contractible auxiliary comes last. This stability is what makes the inventory clinically useful: you can predict, with reasonable confidence, which morpheme should emerge next.