How do you say ''couldn't'' in Hebrew?

Answer 1

Unlike English, Hebrew conjugates for the person in addition to tense. Second, "could" in English could refer to either the past tense or the conditional tense.

So, "he couldn't" as in "he was not able to" is "lo yakhal" (לא יכל).
"He couldn't" as in "he would not be able to" is "lo hayah yekhol" (לא היה יכול).

Answer 2

It depends on the subject and which tense you're referring to. "Couldn't is sometimes used in the present tense. For example:

he couldn't [hit the side of a barn] = הוא לא יכול (hu lo yachol....)

he couldn't [come yesterday] = הוא לא היה יכול (hu lo haya yachol....)

she couldn't [come yesterday] = היא לא היתה יכולה (hi lo hayta yechola...)