to suddenly start laughing
突然笑い出す (totsuzen waraidasu)
"They broke into laughter when the teacher made a joke."
"教師がジョークを言ったとき、彼らは突然笑い出した。" (Kyōshi ga jōku o itta toki, karera wa totsuzen waraidashita.)
to collect your things and prepare to leave
to use knowledge or skills in a real situation
to maintain communication with someone
to look very proud or pleased
to be the first to take action or make a decision
to use money that you had saved
