This is the 444th most frequent Armenian word.
չէին
"Չէին" means "they were not" in English.
In this sentence, "չէին" is used as the past continuous auxiliary verb for forming the negative past continuous tense with the verb "գնացել" (had gone).
Նրանք չէին գնացել դպրոց, որովհետև էր ծանր անձրև։
They hadn't gone to school because it was heavy rain.
Here, "չէի" is the singular first-person auxiliary verb in the past perfect tense, used for forming the negative of the predicate "հասկացել" (realized).
Ես չէի հասկացել, որ բուսական ապուրից սիրում եմ։
I hadn't realized that I like vegetable soup.
In this example, "չէինք" is used as the past perfect negative form for "լսել" (to hear).