couldn't
v. A1 Beginner could·nt
v. the short way to say 'could not'. You use it to say that someone was not able to do something in the past.
v. the contracted form of 'could not'. Expresses a past inability, impossibility, or a polite refusal.
I couldn't find my keys this morning.
The team played well, but they couldn't score a goal before the final whistle.
Despite the investigator's best efforts to locate the original documents, he couldn't find any evidence that the meeting had ever taken place.
From could + n’t.
Usage
A modal contraction followed by the base form of a verb without 'to'.
Pitfall
I couldn't to goI couldn't goThe modal 'couldn't' is followed by the bare infinitive; do not use 'to' before the main verb.