FUNCTIONS OF AUXILIARIES

* They help state and action verbs to realize the CONTINUOUS (BE AUXILIARY) and the PERFECT TENSES (HAVE AUXILIARY)

Example:(present continuous——> I am teaching)/(past continuous—->I was teaching)
(present perfect——> I have eaten) (past perfect—–> she had eaten)

*The HAVE AND BE AUXILIARIES can combine to form the perfect continuous tenses.
Example: (present perfect continuous—–> I have been washing) 

(past perfect continuous——>They had been dancing)

*TO transform the AFFIRMATIVE TO THE NEGATIVE contracted forms for verbs in sentences, questions and TAGS etc.
Negative:/ I like sleeping. I don’t like sleeping./ 

I have drunk tea. I haven’t drunk tea/ 

I was eating cakes-I wasn’t eating cakes.
*QUESTION TAGS:

/ I try skiing. Don’t I?/ I am fat. Aren’t I? We are in Africa. Aren’t we?// He’d better used the tractor. Hadn’t he/
NB. All modals(can, should) also go directly with tags: Let’s go. Shall we? Move faster. Will you?,