*semantics: meaning of words and sentences
ex. Boy and man share many semantic features but differ semantically regarding to age

*phonology: sound system of the language including the sounds that are used and how they combine
ex. constant cluster ski as in the word skirt, but no English words begin with the cluster ksi

*morphology: units of meaning involved in word formation
ex. teacher er meaning "one who" put it on the end of teacher it means "one who teachers"

*pragmatics: the appropriate use of language in different context
ex.using polite language in an appropriate situation

2nd: Babbling which is 2 to 4 months. Babbling consents of cooling and strings of constant vowel combinations such as "ba ba ba ba".
3rd: Infants start to use gestures such as pointing and waking bye bye, or nodding yes and no. This is when the infants is 11 to 12 months.
4th: In the forth milestone they start to say there fist words such as "da da" or "ma ma", or whatever there first words maybe it vary. this is at 13-18 months
5th:To-word utterances. This is by the time the infant reaches 18-24 months. such as "Where cup?" or "My ball".