The main subject, topic, or motif of a discussion, study, work, or project; also used for project themes or slogans.
今日の会議のテーマは予算削減です。
Today's meeting theme is budget cuts.
この映画のテーマは愛と犠牲だ。
The theme of this film is love and sacrifice.
修士論文のテーマをやっと決めた。
I've finally decided on the topic for my master's thesis.