a.

1. 有意義的；意義（或意味）深長的
   I noticed that there has been a significant change on you.

   我注意到你身上發生了有意義的改變。

2. 表示……的[+of]
   Smiles are significant of pleasure.

   微笑表示愉快。

3. 重要的，重大的；值得注意的
   This is one of the most significant studies of the subject.

   這是對該課題最重要的研究之一。

4. 顯著的；有效的；非偶然的

n.[C]【古】

1. 有意義的事物
2. 標誌，象徵

adj.

1. having an unstated meaning; indicative of something.
2. extensive or important enough to merit attention.
3. Statistics  relating to or having significance.