A1 /eɪ / a

A

I. noun

1. the first letter of the alphabet.
2. denoting the first in a set of items, categories, sizes, etc.
3. denoting the first of two or more hypothetical people or things

suppose A had killed B.
4. the highest class of academic mark.

a dazzling array of straight A’s.
5. (in the UK) denoting the most important category of road, other than a motorway

the A34
busy A-roads.
6. denoting the highest-earning socio-economic category for marketing purposes, including top management and senior professional personnel.
7. ( a)
[Chess] denoting the first file from the left, as viewed from White’s side of the board.
8. (usu. a) the first constant to appear in an algebraic expression.
9.
[Geology] denoting the uppermost soil horizon, especially the topsoil.
10. the human blood type (in the ABO system) containing the A antigen and lacking the B.
11. (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.
12. a shape like that of a capital A

[in combination]

an A-shape.
13.
[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.
14. a key based on a scale with A as its keynote.
II. phrases

1. from A to B
from one’s starting point to one’s destination

most road atlases will get you from A to B.
2. from A to Z
over the entire range; completely.

make sure you understand the subject from A to Z.
3. plan A
one’s original plan or strategy

plan A having gone horribly wrong, Ferguson used the interval to change his formation.
Compare with plan B.

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