Speech and language developmental milestones
by age:

6 Months

Vocalization with intonation
Responds to name
Responds to human voices without visual cues by turning head and eyes
Responds appropriately to friendly and angry tones

12 Months
Understands simple instructions, especially if vocal or physical cues are given
Practices inflection
Is aware of the social value of speech

18 Months
Has vocabulary of approximately 5-20 words
Vocabulary is made up of nouns
Some echolalia (repeating a word or phrase over and over)
Jargon with emotional content
Is able to follow simple commands

24 Months
Can name a number of objects common to his or her surroundings
Is able to use at least two prepositions: “in” “on” “under”
Combines words into a short sentence (nouns and verbs)
Average length of sentences is given as 1-2 words
Approximately 2/3 of what child says should be intelligible
Vocabulary consists of approximately 150-300 words
Rhythm and fluency are improving 
Volume and pitch of voice are improving 
Can use two pronouns correctly: I, me, you, although me and I are improving
My and mine are beginning to emerge
Responds to such commands as “show me your eyes (nose, mouth, hair)”

36 Months
Use pronouns I, you, me correctly
Is using some plurals and past tenses
Knows at least three prepositions, usually in, on, under
Knows main body parts and should be able to indicate or name
Handles three word sentences easily
Has in the neighborhood of 900-1000 words
About 90% of what child says should be intelligible
Verbs begin to predominate
Understands most simple questions dealing with his or her environment and activities
Relates his or her experiences so that they can be followed with reason
Able to reason out such questions as “what must you do when you are sleepy, hungry, cool, or thirsty?”
Should be able to give his or her sex, name, age
Should not be expected to answer all questions even though he or she understands what is expected

48 Months
Knows names of familiar animals
Can use at least four prepositions or can demonstrate his or her understanding of their meaning when given commands
Names common objects in picture books or magazines
Knows one or more colors
Can repeat 4 digits when they are given slowly
Can usually repeat words of four syllables
Demonstrates understanding of over and under
Has most vowels, diphthongs and the consonants p, b, m, w, n
Often indulges in make-believe
Extensive verbalization as he or she carries out activities
Readily follows simple commands without stimulus objects in sight
Repetition of words, phrases, syllables, and even sounds

60 Months
Can use many descriptive words spontaneously-both adjectives and adverbs
Knows common opposites: big-little, hard-soft, heavy-light
Has number concepts of 4 or more
Can count to ten
Speech should be completely intelligible, in spite of articulation problems
Should have all vowels and the consonants, m, p, b, h, w, k, g, t, d, n, ng, y
Should be able to repeat sentences as long as nine words in length
Should be able to define common objects in terms of use (hat, shoe, chair)
Should be able to follow three commands given without interruptions
Should know his or her age
Should have simple time concepts: morning, afternoon, night, day, later, after, while, tomorrow, yesterday, today
Should be using fairly long sentences (compound/complex)
Speech should be grammatically correct

6 Years
These additional consonants should be mastered:  f, v, sh, zh, th, and l
Can use and understand past and future tense
Speech should be completely intelligible and socially useful
Should be able to tell a rather connected story about a picture, seeing relationships between objects and events

7 Years
Should have mastered the consonants s-z, r, voiceless th, ch, wh, and soft g
Should handle opposite analogies easily
Understands such terms as: alike, different, beginning, end, etc.
Should be able to tell time to quarter hour
Should be able to do simple reading and writing of many words

8 Years
Can relate past events to future events
Complex and compound sentences should be used easily
Should be few lapses in grammatical constrictions-tense, pronouns, plurals
All speech sounds, including consonant blends should be established
Should be reading with considerable ease and now writing simple compositions
Social amenities should be present in his or her speech in appropriate situations
Control of rate, pitch, and volume are generally well and appropriately established
Can carry on conversation at rather adult level
Follows fairly complex directions with little repetition
Has well developed time and number concepts