a

noun, often capitalized, often attributive

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\ ˈā

plural a's or as\ ˈāz

Definition of a

(Entry 1 of 13)

1a : the 1st letter of the English alphabet

b : a graphic representation of this letter

c : a speech counterpart of orthographic a

2 : the sixth tone of a C-major scale

3 : a graphic device for reproducing the letter a

4 : one designated a especially as the first in order or class

5a : a grade rating a student's work as superior in quality

b : one graded or rated with an A

6 : something shaped like the letter A

7 capitalized : the one of the four ABO blood groups characterized by the presence of antigens designated by the letter A and by the presence of antibodies against the antigens present in the B blood group

indefinite article

\ ə, for emphasis (ˈ)ā

, Canadian ˈa

Definition of a (Entry 2 of 13)

1 —used as a function word before singular nouns when the referent is unspecified a man overboard and before number collectives and some numbers a dozen

2 : the same birds of a feather swords all of a length

3a —used as a function word before a singular noun followed by a restrictive modifier a man who was here yesterday

b : any a person who is sick can't work

c —used as a function word before a mass noun to denote a particular type or instance a bronze made in ancient times

d —used as a function word before a proper noun representing an example or type the attractions of a Boston or a Cleveland

e —used as a function word before a proper noun to indicate limited knowledge about the referent a Mr. Smith called to inquire about the job

f —used as a function word before a proper noun to distinguish the condition of the referent from a usual, former, or hypothetical condition a triumphant Ms. Jones greeted her supporters

g —used before the name of a day of the week to refer to one occurrence of it Christmas falls on a Tuesday this year.

h —used before the name of a person (such as a famous artist) when the name is being used to refer to something (such as a painting) created by that person Her violin is a Stradivarius.

i —used before a family name to show that someone is a member of that family To be a Kennedy is to lead two lives …— Margaret Carlson

4 —used as a function word with nouns to form adverbial phrases of quantity, amount, or degree felt a bit tired

preposition (1)

\ ə also (ˈ)ā

Definition of a (Entry 3 of 13)

1 : in, to, or for each twice a week

2 chiefly dialectal : on, in, at

preposition (2)

\ ə \

Definition of a (Entry 4 of 13)

: of —often attached to the preceding word kindalotta

verb

\ ə, (ˌ)a

Definition of a (Entry 5 of 13)

archaic

: have I might a had husbands afore now— John Bunyan

abbreviation (1)

Definition of a (Entry 6 of 13)

1 absent

2 acceleration

3 acre

4 adult

5 alto

6 chemistry amorphous —usually used in combination a-Si

7 anode

8 answer

9 ante

10 anterior

11 are

12 area

13 atto-

14 author

prefix (1)

\ ə \

Definition of a- (Entry 7 of 13)

1 : on : in : at abed

2 : in (such) a state or condition afire

3 : in (such) a manner aloud

4 : in the act or process of gone a-hunting atingle

prefix (2)

\ (ˈ)ā also (ˈ)a or (ˈ)ä \

variants: or an- \ (ˈ)an \

Definition of a- (Entry 8 of 13)

: not : without asexual —a- before consonants other than h and sometimes even before h, an- before vowels and usually before h achromaticahistoricalanastigmaticanhydrous

-a-

combining form

Definition of -a- (Entry 9 of 13)

: replacing carbon especially in a ring aza-

-a

noun suffix

\ ə \

Definition of -a (Entry 10 of 13)

: oxide silica

abbreviation (2)

Definition of A (Entry 11 of 13)

1 ace

2 adenine

3 ampere

symbol

Definition of A (Entry 12 of 13)

argon

abbreviation (3)

Definition of Å (Entry 13 of 13)

angstrom

A vs. an: Usage Guide Example Sentences Learn More about a

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A vs. an: Usage Guide

Indefinite article

In speech and writing a is used before a consonant sound. a door a human Before a vowel sound an is usual an icicle an honor but especially in speech a is used occasionally, more often in some dialects than in others. a apple a hour a obligation Before a consonant sound represented by a vowel letter a is usual a one a union but an also occurs though less frequently now than formerly. an unique such an one Before unstressed or weakly stressed syllables with initial h both a and an are used in writing. a historic an historic In the King James Version of the Old Testament and occasionally in writing and speech an is used before h in a stressed syllable. an huntress an hundred children are an heritage of the Lord — Psalms 127:3 (King James Version)

Examples of a in a Sentence

Noun a word that begins with an a a word that begins with a a song in the key of A She got an A on the exam.

First Known Use of a

Noun

before the 12th century, in the meaning defined at sense 1a

Indefinite article

before the 12th century, in the meaning defined at sense 1

Preposition (1)

before the 12th century, in the meaning defined at sense 2

Preposition (2)

15th century, in the meaning defined above

Verb

14th century, in the meaning defined above

History and Etymology for a

Indefinite article

Middle English, from Old English ān one — more at one

Preposition (1)

Middle English, from Old English a-, an, on

Preposition (2)

Middle English, by contraction

Verb

Middle English, contraction of have

Prefix (1)

Middle English, from Old English

Prefix (2)

Latin & Greek; Latin, from Greek — more at un-

Combining form

perhaps from -a- in ring compounds such as thiazole (in which -a- is the initial of azole)

Noun suffix

New Latin, from -a (as in magnesia)

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More Definitions for a

noun

English Language Learners Definition of a

(Entry 1 of 2)

: the first letter of the English alphabet

: a musical note or key referred to by the letter A : the sixth tone of a C-major scale

: a grade that is given to a student for doing excellent work

indefinite article

English Language Learners Definition of a (Entry 2 of 2)

—used before singular nouns when the person or thing is being mentioned for the first time

—used like one before number words like hundred, thousand, etc.

—used like one before number words like third, fortieth, etc.

See the full definition for a in the English Language Learners Dictionary

noun, often capitalized

\ ˈā

plural a's or as\ ˈāz \

Kids Definition of a

(Entry 1 of 3)

1 : the first letter of the English alphabet

2 : a grade that shows a student's work is excellent

3 : a musical note referred to by the letter A

indefinite article

\ ə

, ˈā \

Kids Definition of a (Entry 2 of 3)

1 : someone or something being mentioned for the first time There's a dog in the yard.

2 : the same two of a kind

3 : any entry 1 sense 1 It's hard for a person to understand.

4 : for or from each an apple a day The new theater charges ten dollars a person.

5 : one entry 2 sense 3 a dozen doughnuts a week This is a third the size of that.

Hint: A is used before words that do not begin with a vowel sound.

prefix

\ ə \

Kids Definition of a-

1 : on : in : at abed

2 : in (such) a state, condition, or manner afire aloud

3 : in the act or process of gone a-hunting

abbreviation

Medical Definition of a

(Entry 1 of 4)

1 about

2 absent

3 absolute

4 absorbency; absorbent

5 accommodation

6 acetum

7 acid; acidity

8 actin

9 active; activity

10 allergist; allergy

11 alpha

12 anode

13 answer

14 ante

15 anterior

16 aqua

17 area

18 artery

19 asymmetric; asymmetry

noun

\ ˈā

Medical Definition of A (Entry 2 of 4)

: the one of the four ABO blood groups characterized by the presence of antigens designated by the letter A and by the presence of antibodies against the antigens present in the B blood group

abbreviation

Medical Definition of A (Entry 3 of 4)

1 adenine

2 ampere

symbol

Medical Definition of Å (Entry 4 of 4)

angstrom