a

noun, often capitalized, often attributive
\ ˈā How to pronounce a (audio) \
plural a's or as\ ˈāz How to pronounce as (audio) \

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
\ ə, for emphasis (ˈ)ā How to pronounce a (audio) , Canadian ˈa \

Definition of a (Entry 2 of 13)

1 used as a function word before singular nouns when the referent is unspecifieda man overboard and before number collectives and some numbersa 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 modifiera 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 instancea bronze made in ancient times
d used as a function word before a proper noun representing an example or typethe attractions of a Boston or a Cleveland
e used as a function word before a proper noun to indicate limited knowledge about the referenta 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 conditiona triumphant Ms. Jones greeted her supporters
g used before the name of a day of the week to refer to one occurrence of itChristmas 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 personHer violin is a Stradivarius.
i used before a family name to show that someone is a member of that familyTo 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 degreefelt a bit tired

a

preposition (1)
\ ə also (ˈ)ā How to pronounce a (audio) \

Definition of a (Entry 3 of 13)

1 : in, to, or for each twice a week
2 chiefly dialectal : on, in, at

a

preposition (2)
\ ə \

Definition of a (Entry 4 of 13)

: of often attached to the preceding wordkindalotta
\ ə, (ˌ)a How to pronounce a (audio) \

Definition of a (Entry 5 of 13)

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

a

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 combinationa-Si
7 anode
8 answer
9 ante
10 anterior
11 are
12 area
13 atto-
14 author

a-

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

a-

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 hachromaticahistoricalanastigmaticanhydrous

Definition of -a- (Entry 9 of 13)

: replacing carbon especially in a ring aza-
\ ə \

Definition of -a (Entry 10 of 13)

: oxide silica

A

abbreviation (2)

Definition of A (Entry 11 of 13)

1 ace
2 adenine
3 ampere

Definition of A (Entry 12 of 13)

argon

Å

abbreviation (3)

Definition of Å (Entry 13 of 13)

angstrom unit

Keep scrolling for more

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.
See More

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)

Keep scrolling for more

Learn More about a

Time Traveler for a

Time Traveler

The first known use of a was before the 12th century

See more words from the same century

Statistics for a

Cite this Entry

“A.” The Merriam-Webster.com Dictionary, Merriam-Webster Inc., https://www.merriam-webster.com/dictionary/a's. Accessed 9 December 2019.

Keep scrolling for more

More Definitions for a

How to pronounce Å (audio)

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
How to pronounce Å (audio)

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.

a

noun, often capitalized
\ ˈā How to pronounce a (audio) \
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
\ ə How to pronounce a (audio) , 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.
\ 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

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
\ ˈā How to pronounce A (audio) \

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

Medical Definition of A (Entry 3 of 4)

1 adenine
2 ampere

Medical Definition of Å (Entry 4 of 4)

angstrom

Keep scrolling for more

More from Merriam-Webster on a

Rhyming Dictionary: Words that rhyme with a

Spanish Central: Translation of a

Nglish: Translation of a for Spanish Speakers

Britannica English: Translation of a for Arabic Speakers

Comments on a

What made you want to look up a? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

contradictory or incongruous words

Get Word of the Day daily email!

Test Your Vocabulary

Semantic Drift Quiz

  • a twisty river
  • Which of the following was once a synonym for fun?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Add Diction

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!