a

adj.一,一个,一只,一件.

I have engaged a room at this hotel.
我已经在这个旅馆里预订了一个房间。
You should give it a try.
你应该试一试。
I don't care what a car looks like as long as it gets me from A to B.
我倒不在乎汽车的样子, 只要能把我从一处载到另一处就行了.
The function of an adjective is to describe or add to the meaning of a noun.
形容词的作用是描述或增加名词的意思。
China is a developing country.
中国是一个发展中国家。
You're just a good for nothing bum!
你一无是处！
Declension means varying the forms of nouns, pronouns and adjectives in a sentence.
变格是指名词、代词和形容词在句中的形式变化。
Would you do me a favor?
你能帮我一个忙吗？

名词复数:a's

名词 a:

a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
同义词：angstrom, angstrom unit
any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
同义词：vitamin A, antiophthalmic factor, axerophthol
one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
同义词：deoxyadenosine monophosphate
(biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
同义词：adenine
the basic unit of electric current adopted under the Systeme International d'Unites
同义词：ampere, amp
the 1st letter of the Roman alphabet
同义词：letter a
the blood group whose red cells carry the A antigen
同义词：type A, group A