an的用法an用在以元音字母（a，e，i，o，u）开头，或以不发音的h字母开头的单词前面，如an apple一个苹果，an island一个岛，an uncle一位大叔。an还用在发音以元音开头的单个字母前面，如an MP一个国会议员。
an的例句He had been spotted by an alert neighbour（一个警觉的邻居发现了他）；He had been patiently waiting in the anteroom for an hour（他在前厅耐心地等了一个小时）。
