(亦作a)
(pl. As 或 A's /eɪz/)
1
- the first letter of the alphabet英语字母表中第一个字母。
1.1
- denoting the first in a set of items, categories, sizes, etc.甲,A项, A类, A号（一组项目、分类或尺码等的第一位）。
1.2
- denoting the first of two or more hypothetical people or things（假设的第一人或第一例）A, 甲：
suppose A had killed B.
假设甲杀死了乙。
1.3
- the highest class of academic mark（学业成绩）A等, 甲等。
1.4
- (in the UK) denoting the most important category of road, other than a motorway（英国）干线公路（非高速公路）：
the A34
34号干线
busy A-roads.
繁忙的干线公路。
1.5
- denoting the highest-earning socio-economic category for marketing purposes, including top management and senior professional personnel（为市场营销而划分的社会经济类别中的）最高收入群体（包括高层管理层和高级专业人员）。
1.6
a
Chess denoting the first file from the left, as viewed from White's side of the board【棋】（从执白方左边数过来的）第一列。
1.7
- （一般作 a）the first constant to appear in an algebraic expression（代数表达式中的）第一已知量。
1.8
- Geology denoting the uppermost soil horizon, especially the topsoil【地质】表层土壤。
1.9
- the human blood type (in the ABO system) containing the A antigen and lacking the B.A型血。
1.10
- with numeral denoting a series of international standard paper sizes each twice the area of the next, as A0, A1, A2, A3, A4, etc., A4 being 210 × 297 mm.A型号纸（国际标准纸张型号代号, 如A0, A1, A2, A3, A4等, 每一号的面积是下一号的两倍, A4号纸为210×297毫米）。
2
- a shape like that of a capital A.A字形：
in combination an A-shape.A字形。参见
A -FRAME,A -LINE.
3
- Music the sixth note of the diatonic scale of C major. The A above middle C is usually used as the basis for tuning and in modern music has a standard frequency of 440 Hz.【乐】A音, A调（C大调音阶的第六音）。
3.1
- a key based on a scale with A as its keynote.A音键。
短语
from A to B
- from one's starting point to one's destination从出发地到目的地：
most road atlases will get you from A to B.
大部分道路图册都可以让你自出发地到达目的地。
from A to Z
- over the entire range; completely从头至尾, 完全地。
1.1
- ace (used in describing play in bridge and other card games).用于描述桥牌或其他纸牌游戏的玩法同ACE:
you cash ❤AK.
你出红心AK.
1.2
- against (heading the column in a table of sports results which shows the goals or points scored against each club).［在体育项目比分表上表示与每个俱乐部的比分］同AGAINST.
1.3
- informal A level.〈非正式〉同 A LEVEL.
1.4
- ampere(s).同AMPERE或amperes.
1.5
Å
ångstrom(s).同ÅNGSTROM或ångstroms.
1.6
- answer.同ANSWER:
Q: What is a hung parliament? A: One in which no single party has an overall majority.
问：什么是均势议会？答：即没有一个党派占大多数议席的议会。
1.7
- (in names of sports clubs) Athletic.［用于体育俱乐部名称中］同Athletic:
Dunfermline A.
邓弗姆林体育俱乐部。
1.8
- Austria (international vehicle registration).同AUSTRIA（国际车辆注册用语）。