Cases of word usage

1) to give the forms of (a verb) for numbers, tense etc (conjugate)

2) (used with the past participle of another verb (e.g. moved, done) to form) a: the present perfect tense, b: the past perfect tense, c: the future perfect tense, d: the perfect conditional tense (have)

3) used as the past tense form of 'shall' (should)

4) extremely tense or nervous (uptight)

5) (used as the past tense form of 'will' especially in reported speech and to express refusal); (used to report regular or usual behaviour in the past); (used to express the conditional) (would)