This is the 5th most frequent Estonian word.
oli
"Was" (past tense of "to be").
In this example, 'oli' is the third-person singular past tense of 'olla' and functions to form a question about possession in the past.
Kas see oli sinu auto?
Was that your car?
In this sentence, 'oli' is the third-person singular past tense of the verb 'olla', which means 'to be' in Estonian. It is used to describe a state or condition in the past.
Päike oli taevas kõrgel.
The sun was high in the sky.
Here, although 'oli' itself isn't present, 'olin' is its first-person singular past tense form, derived from 'olla'. It is used to describe a personal state or condition in the past.