didn't
v.v. the short way to say 'did not'. You use it to talk about something that did not happen in the past.
v. the contracted form of 'did not', functioning as a negative auxiliary verb in the past simple tense. Used to negate a main verb or to provide a short negative answer.
I didn't see the movie last night.
She didn't finish her homework on time because she was feeling unwell.
While the team didn't achieve their primary objective, the data they gathered during the trial proved invaluable for future research and development.
did + -n't.
Followed by the base form of the main verb (infinitive without 'to'). In formal writing, the uncontracted 'did not' is generally preferred.
I didn't went to the storeI didn't go to the storeAfter the auxiliary 'didn't', the main verb must be in its base form, not the past tense.