是說

In a sentence

• 這部電影是說一個年輕男子的成長故事。

  This movie is about the coming-of-age story of a young man.

  In this sentence, '是說' indicates what the movie is about, functioning similarly to 'is about.'

• 他昨天沒來上課，是說他身體不舒服。

  He didn't attend class yesterday, which is to say he wasn't feeling well.

  '是說' in this context serves to elaborate or state a reason for the first clause.

• 我記得你是說會帶一本書來給我，是嗎？

  I remember you said you would bring me a book, right?

  Here, '是說' is used to preface a recollection of something someone mentioned or intended.