ichidan verb
begin to speak; start talking
Used when someone starts speaking after a pause, or when a topic is brought up. The verb is a compound of 話す (to speak) and 始める (to begin).
彼は突然話し始めた。
He suddenly began to speak.
先生が教室に入ると、生徒たちは話し始
When the teacher entered the classroom, the students started talking.