Functions 0-9 months: Mainly instrumental and regulatory
Phonology: Babbling and basic intonation patterns emerge even pre-verbally
Reduplication may be common e.g. baba, nana
Functions 9-18 months: Interactional, instrumental and regulatory functions served by verbal as well as non-verbal utterances
Much naming of people and objects in immediate environment. Meanings are context and phonology dependent.
Functions 18 months - 2 years: May start to include representational language (exchanges of information)
Lexis/Semantics: Much classification. Spatial location (up/down, in/out etc) and attributes of objects (hot, cold, big, small etc)
Functions 2-21/2 years: more complex requests
Phonology: Vowel sounds becoming more consistent; reduplication disappears. Intonation, stress and other prosodic features continue to develop.
Functions 21/2- 3 years: Requests for explanations (why?!) may mark increasingly heuristic and imaginative functions. Indirect requests such as 'Can I have?'
Phonology: continuing stabilisation of phonemic and prosodic aspects, though some consonants (such as l, r, th) still not acquired: e.g. 'three' where 'f' is likely to be substituted for 'th'.
Functions 3-31/2 years: A full range now, including representing feelings and attitudes
Lexis/semantics: conditional and hypothetical meanings (what if ...). Specific references to time past, present and future.
Functions: 31/2 - 4 years: Continuing developent in sophisticated interactional, heuristic and imaginative language functions.
Lexis/semantics: Continuing development in ability to use more precise, abstract and varied vocabulary.