Voice \ Tense / Mood
If a transitive verb is in the active voice, then the subject will always be the one doing the action.
Ex: The crocodile waited in the swamp for its prey.
Ex: The crocodile snapped its jaws at the passing bird. The crocodile is the one doing the action of snapping, so the verb is in the active voice.
When a transitive verb is in the passive voice, then the subject will always be the receiver of the action, and the action will usually start with a form of 'was'.
Ex: The cannon was fired by the British soldier. /The British soldier was the one who was doing the firing, and the cannon is receiving that action./
Ex: The British ship was attacked by pirates. /The pirates are doing the attacking, so the British ship is receiving that action./
The progressive tense always has some form of 'be' + the present participle of the main verb.
Forms of 'Be': are, am, is, was, were, will be
Present Progressive: My dogs are always playing with each other.
Past Progressive: My dogs were hiding from us the first time we tried giving them a bath.
Future Progressive: My dogs will be having fun all day while I'm at school.
The perfect tense always has some form of 'have' + the past participle of the main verb.
Forms of 'have': will have, has, have, had
Present Perfect: Tanks have served great use in the military for almost 100 years.
Past Perfect: The tank had been used for the first time in World War I.
Future Perfect: Tanks will have improved even more by next year.
The emphatic mood is a verb that gives special force to a simple or past tense verb. In the present form, you would use 'do' or 'does' before the main verb. In the past tense, you would use 'did' before the main verb.
The anglerfish does live in the deepest part of the ocean: the twilight zone.
Tiger sharks do eat almost anything, all the way from garbage, to birds, to other sharks.
The first sharks did appear around 55-85 million years after the first fish that existed.