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

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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From the Editors at Merriam-Webster

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Cite this Entry

“A.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/a. Accessed 19 Aug. 2022.

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More Definitions for a

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