This is the 449th most frequent Russian word.
начал
"Начал" means "began" or "started" in English.
The word 'начал' is used in the past tense masculine singular to indicate the initiation of an action.
Он начал читать новую книгу.
He started reading a new book.
The word 'начала' is used in the past tense feminine singular form to match the subject of the sentence.
Она начала готовить ужин.
She started preparing dinner.
The word 'начали' here is in the past tense plural form to agree with the plural subject.