1. Verbs

2. ACTION VERBS: Tells what the subject does or did.
Ex. Mark runs around the field.
Mark ran around the field.
Examples of action verbs:
walked
wrote

3. LINKING VERBS: Links(connects) subject to rest of sentence
Ex. Mark is friendly.
Mark was friendly.
is, are, was, were, am, have been, has been, had been, will be, should be, etc.

4. HELPING VERBS: Help action verbs
Ex. Mark will eat his lunch.
Mark has eaten his lunch.
Mark should eat his lunch.
will, may, could, can, have, should, shall, would, must, etc.