在多數(shù)情況下,抽象名詞都用于單數(shù)形式,并不加任何冠詞：
Knowledge is power.知識就是力量.
Failure is the mother of success.失敗是成功之母.
但有時也可加定冠詞the或不定冠詞a或an：
a.I did not have the courage to tell you.我沒有勇氣告訴你.
b.It is a pleasure to help you .我很樂意幫你.
c.We have a great respect for the professor.我們很尊重教授.
有些抽象名詞也可用作個體名詞,代表具體的東西,這時它可以加不定冠詞,也可用于復(fù)數(shù)形式：
What are the principles of democracy?什么是民主的原則?
A true democracy allows free speech.真正的民主國家允許言論自由.