主要是看音标，单词的发音是元音开头就用an，是辅音就用a.
u开头前面用an的单词：uncomfortable、ugly、umbrella 等。
扩展资料
例句：
“Boredom could be an uncomfortable feeling,” she said.
“无聊可能是一种不舒服的.感觉,”她说。
The decree put the president in an uncomfortable position.
这一判决使总统陷入了尴尬的处境中。
An ugly new building blocked the view from the window.
一座难看的大楼把窗外的景物遮住了。
Its not worth bothering with an umbrella ─ the cars just outside.
不必打伞——汽车就停在外面。
It was raining hard, and she hadnt an umbrella.
雨下得很大，但她没有雨伞。
