a

音標(biāo)發(fā)音

通常來(lái)說(shuō)，a 是用在以輔音開(kāi)首的詞前面，an 是用在以元音開(kāi)首的詞前面；
可數(shù)名詞前面用 a（或 an），不可數(shù)名詞前面不可用a（或 an)，如可以說(shuō) a healthy boy，卻不可以說(shuō) a health；
在特定情況下，a（或 an）可以用在復(fù)數(shù)形式前面:習(xí)語(yǔ)中有a few (books)，a great many (books)等表示方法。在表示時(shí)間或款項(xiàng)的短語(yǔ)前面，如 a further five minutes。在若干在形式上是復(fù)數(shù)而在意思上是單數(shù)的單詞前面，如 a barracks，a links。在美國(guó)口語(yǔ)中，如 a good ways，a long ways；
a（或 an）有時(shí)有“一個(gè)而不是那所要的一個(gè)”的意思。a 也有“任何一個(gè)”的意思。I got a letter indeed，but it was from a friend. 事實(shí)上，我收到了一封信，但只是一個(gè)朋友的來(lái)信。I wanted to read a book，I did not care whether it was a history，a novel，or a biography.
a 與 few 搭配使用時(shí)，few 是“很少”，有“幾乎沒(méi)有”的意思。a few 是“若干”，有“頗有幾個(gè)”的意思。注意，only a few 卻等于 few，也是“很少”的意思。

Liver and kidney are particularly rich in vitamin A.
肝臟和腎臟富含維生素A。
Details are available from the Hon. Sec. A.R. Bushby.
詳情可咨詢名譽(yù)秘書(shū)A.R.布什比。
I was assigned to Troop A of the 10th Cavalry.
我被派往第10騎兵隊(duì)的A連。
He brought me a large package.
他給我送來(lái)一個(gè)大包裹.
He missed the first prize by a whisker.
他和頭獎(jiǎng)擦肩而過(guò).

(NOT PARTICULAR) used before a noun to refer to a single thing or person that has not been mentioned before, especially when you are not referring to a particular thing or person
(ONE) one

You use a or an when you are referring to someone or something for the first time or when people may not know which particular person or thing you are talking about.
You use a or an when you are referring to any person or thing of a particular type and do not want to be specific.
You use a or an in front of an uncount noun when that noun follows an adjective, or when the noun is followed by words that describe it more fully.
You use a or an in front of a mass noun when you want to refer to a single type or make of something.
You use a in quantifiers such as a lot, a little, and a bit. (a lot), (a little), (a bit##bit)
You use a or an to refer to someone or something as a typical member of a group, class, or type.
You use a or an in front of the names of days, months, or festivals when you are referring to one particular instance of that day, month, or festival.
You use a or an when you are saying what someone is or what job they have.
You use a or an instead of the number "one," especially with words of measurement such as "hundred," "hour," and "metre," and with fractions such as "half," "quarter," and "third." (one)
You use a or an in expressions such as eight hours a day to express a rate or ratio.
&rarran informal or dialect word for have
&rarr(usually linked to the preceding noun) an informal form of of
acceleration