11. Auxiliary Verbs

Auxiliary or Helping Verbs are used with main verb to give grammatical meaning to the sentence.

Features:

1. They help to form different tenses, moods, voices or add emphasis.
2. It helps the main verb, as the main verb cannot stand alone to give complete meaning to the sentence.
3. They are used to form questions & negatives.
4. Auxiliary verbs change their forms to express different tenses.
5. These verbs can be used as main verb (linking verb) but they are not action verbs.

Examples:

1. Sam is playing in the garden.
2. Are they coming for the party?
3. She doesn't know the purpose of their visit.

Here,

1. 'Playing, coming, know' are the main verbs. 
2. 'Is, are, doesn't ' are the auxiliary verbs. 
3. They are helping the main verbs, without which the sentence will be incomplete.

Example:

1. Tom is swimming in the pool.

Here, the verb 'is' is used as an auxiliary verb.

2. Tom is in the pool.

Here, 'is' is used as a main verb i.e. linking verb & not auxiliary verb.