a.

1. 複雜的；難懂的；結構複雜的
   a complicated machine

   結構複雜的機器

   That puzzle is too complicated for the children.

   那個謎語對兒童來說太難了。

1. complicate的動詞過去式、過去分詞

adj.

1. consisting of many interconnecting parts; intricate.
   ▸involving many different and confusing aspects.
2. Medicine  involving complications.