Brown's 14 Grammatical Morphemes
Complete reference for all 14 morphemes — ordered by acquisition stage, with mastery criteria and LSA scoring guidance.
Brown's Stage II
Present Progressive -ing
Present progressive -ing is the first of Brown's 14 grammatical morphemes that English-speaking toddlers master, typically between 19 and 28 months of age.
View detailsPreposition "in"
The locative preposition "in" is the second of Brown's 14 morphemes, typically mastered between 27 and 30 months alongside its sibling "on".
View detailsPreposition "on"
The locative preposition "on" is the third of Brown's 14 morphemes, mastered alongside "in" between 27 and 30 months in typical development.
View detailsRegular Plural -s
Regular plural -s is the fourth of Brown's 14 morphemes, marking countable noun plurality and reaching mastery between 27 and 33 months.
View detailsIrregular Past Tense
Irregular past-tense verbs ("went", "ate", "broke") are the fifth of Brown's 14 morphemes, mastered between 25 and 46 months in typical development.
View detailsPossessive 's
Possessive 's is the sixth of Brown's 14 morphemes, marking noun possession and mastered between 26 and 40 months in typical development.
View detailsBrown's Stage III
Uncontractible Copula
Uncontractible copula 'be' is the seventh of Brown's 14 morphemes, mastered between 27 and 39 months in obligatory non-contractible contexts.
View detailsArticles ("a", "the")
The articles "a" and "the" are the eighth of Brown's 14 morphemes, mastered between 28 and 46 months as children learn definite versus indefinite reference.
View detailsBrown's Stage IV
Regular Past -ed
Regular past tense -ed is the ninth of Brown's 14 morphemes, marking past on regular verbs and reaching mastery between 26 and 48 months.
View detailsRegular Third-Person Singular -s
Regular third-person singular -s is the tenth of Brown's 14 morphemes, marking present-tense agreement and reaching mastery between 26 and 46 months.
View detailsBrown's Stage V
Irregular Third-Person Singular
Irregular third-person singular forms (does, has) are the eleventh of Brown's 14 morphemes, mastered between 28 and 50 months.
View detailsUncontractible Auxiliary
Uncontractible auxiliary 'be' is the twelfth of Brown's 14 morphemes, mastered between 29 and 48 months in obligatory non-contractible contexts.
View detailsBrown's Stage V+
Contractible Copula
Contractible copula 'be' is the thirteenth of Brown's 14 morphemes, mastered between 29 and 49 months in obligatory contractible contexts.
View detailsContractible Auxiliary
Contractible auxiliary 'be' is the fourteenth and last of Brown's 14 morphemes, mastered between 30 and 50 months and the last to reach criterion.
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