Perfect Tense

• PERFECT TENSE

Perfect tense is used for describing a past actions effect on the present : He has arrived. Now he is here.
This is holds true for events that have just been secluded as well as for events that have not yet occured.

Perfect tense is formed by combining have/has with the main verb past participle form :
a. I have arrived
   A negation is produced by inserting not after have/has
b. I have not arrived
   Question in present perfect are formulated by starting a sentences with have/has
c. Has she arrived ?

• PAST PERFECT TENSE

1. Past perfect tense is a kind of tense that is used to describe an action or an event that started in a certain time in the past and completed or finished till certain time in the past too.Or,
2. Past perfect tense is used to to express an action or an event that had happened before the other vent or action happened.

The pattern :
(+) subject + had + verb III + complement
(-) subject + had + not + verb III + complement
(?) had + subject + ver III + complement + ?

Example :
(+) We had eaten before they came
(-) We had not eaten before they came
(?) Had we eaten before they came ?

Adverb used :
From 1987 to 1989, once, twice, etc....