a
英音: [ei,ə] 美音: [ei,ə]art.
1.（非特指的）一（个）
2.（同类事物中）任何一个
3.每一（个）
4.某一种
5.（用于某些物质名词前）一种
6.（=the same）同一（个）
7.（与否定词连用，相当于any）
8.【口】（用于虚拟语气，=have）
pron.【方】
1.他，她，它
2.他们，她们，它们
3.我
abbr.
1.（用于旅行时刻表）arrive
2.（用于日期前）before
英英释义
- (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
- one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
- any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
- the basic unit of electric current adopted under the Systeme International d'Unites
- a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
- the blood group whose red cells carry the A antigen
- the 1st letter of the Roman alphabet
