a.

1. 首要的，主要的
   A primary cause of Tom's failure is his laziness.

   懒惰是汤姆失败的主要原因之一。

2. 初级的，初等的；基层的[Z][B]
   I started primary school when I was 5 years old.

   我五岁时开始读小学。

3. 最初的；原始的[Z][B]
   The historian searched for primary sources of information about the past.

   历史学家寻找有关过去的原始资料来源。

4. 基本的；本来的[Z][B]
   The primary meaning of the word isn't used now, but you can look it up in a big dictionary.

   这个字的本义现在不用了，但你可以在大字典里查到。

n.[C]

1. （次序，质量等）居首位的事物
2. 原色
3. 【主美】候选人选拔会；初选
   We lost the New Hampshire primary.

   我们在新罕布什尔州的初选失利了。

adj.

1. of chief importance; principal.
2. earliest in time or order.
   ▸ (Primary) Geology  former term for Palaeozoic.
3. not caused by or based on anything else.
4. chiefly Brit. relating to or denoting education for children between the ages of about five and eleven.
5. of or denoting the input side of a transformer or other inductive device.
6. Chemistry  (of an organic compound) having its functional group on a carbon atom bonded to no more than one other carbon atom.
   ▸derived from ammonia by replacement of one hydrogen atom by an organic group.

n.

1. (in the US) a preliminary election to appoint delegates to a party conference or to select the candidates for a principal, especially presidential, election.
2. Astronomy  the body orbited by a smaller body.