Would is usually followed by an infinitive without ‘to’: A picnic would be nice. Sometimes it is used without a following infinitive: ♦ They didn’t do as much as they said they would.
In conversation and informal writing, would is often shortened to ’d: I thought you’d like a drink before dinner.
Would does not change its form, so the third person singular form does not end in ‘-s’: As a child, she would often run away from home.
Questions and negatives are formed without ‘do’: Would you like a cup of coffee? ♦ He would not tell us his secret.
The negative form would not is often shortened in conversation or informal writing to wouldn’t: I wouldn’t want to have your job.
Would is often used in question tags: You wouldn’t lie to me, would you?
Would has no tenses, no participles, and no infinitive form.
There is no past tense, but would have followed by a past participle can be used for talking about actions that did not happen: She would have bought the house if she had been able to afford it (=she did not buy it).
In some cases would can be used as the past tense of will, for example in indirect speech introduced by a verb in the past tense: I promised that I would visit her the next day.