请问百度词典后跟的[C]、[U]什么意思?

问题描述:

请问百度词典后跟的[C]、[U]什么意思?
我来给个例子!
我搜索:heart.
heart
KK:[]
DJ:[]
n.
1.心脏;胸[C]
The boy's heart gave a jump.
这男孩的心猛地一跳.
2.内心;心肠[C]
He has a cold heart.
他冷酷无情.
3.感情;爱情;爱好[U]
She gave her heart to him.
她真心爱他.
4.心形的东西[C]
She wore a diamond heart around her neck.
她脖子上佩带着一颗心形的钻石.
5.(纸牌的)红心[C]
6.中心;要点[the S][(+of)]
Let's get to the heart of the problem.
让我们来谈谈问题的核心吧.
7.勇气;精神[U]
I didn't have the heart to tell you about it.
我没有勇气将此事告诉你.
7.勇气;精神[U]这个后面跟的U是什么意思?

c可数名词countable noun
u不可数名词uncountable noun