1- use with nouns not mentioned before.
2- use to mean any one Ex. a horse
3- Use with an abstract countable noun restricted by an adjective or a phrase Ex. he has a good knowldge of french
4-use after a negative to mean one single. Ex. He did not say a word
5- use instead of (one) before particular numbers and fractions Ex . a 1/f(fifth) , a1000 (thousand)
6- use to mean (to) , or (for) or (each) or (per) Ex. pay SR3:00 a gallon
7_use to show membership of a class EX. He is a doctor
8- use in the structure ( N + of +poss .det. +n +`s) EX. He is a friend of my father`s.
Thanx Muteb for the useful information
Allah bless u um basmah
thanks a lot muteb
welcome بسلم جروح