themes
A theme in a piece of writing, a talk, or a discussion is an important idea or subject that runs through it.
topic , subject , motif
The theme of the conference is renaissance Europe.
该会议的主题是文艺复兴时期的欧洲。
A theme is a short simple tune on which a piece of music is based.
variations on themes from Mozart's The Magic Flute.
莫扎特的《魔笛》中主旋律的变奏曲。
Theme music or a theme song is a piece of music that is played at the beginning and end of a film or of a television or radio programme.
the theme from Dr Zhivago.
《日瓦戈医生》的主题曲。