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a 1 or A (ā)
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n. pl. a's or A's also as or As
1. The first letter of the modern English alphabet.
2. Any of the speech sounds represented by the letter a.
3. The first in a series.
4. Something shaped like the letter A.
5. A The best or highest in quality or rank: grade A milk.
6. Music
a. The sixth tone in the scale of C major or the first tone in the relative minor scale.
b. A key or scale in which A is the tonic.
c. A written or printed note representing this tone.
d. A string, key, or pipe tuned to the pitch of this tone.
7. A One of the four major blood groups in the ABO system. Individuals with this blood group have the A antigen on the surface of their red blood cells, and the anti-B antibody in their blood serum.
Idiom:
from A to Z
Completely; thoroughly.
(click for a larger image)
Marquee, Radio City Music Hall
Opened in 1932, Radio City Music Hall is a landmark in New York's Rockefeller Center.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a- 1 or an-
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pref.
Without; not: amoral.


The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a 2 (ə; āwhen stressed)
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indef.art.
1. Used before nouns and noun phrases that denote a single but unspecified person or thing: a region; a person.
2. Used before terms that denote number, amount, quantity, or degree: only a few of the voters; a bit more rest; a little excited.
3.
a. Used before a proper name to denote a type or a member of a class: the wisdom of a Socrates.
b. Used before a mass noun to indicate a single type or example: a dry wine.
4. The same: birds of a feather.
5. Any: not a drop to drink.

[Middle English, variant of an, an; see AN1.]

Usage Note: In writing, the form a is used before a word beginning with a consonant sound, regardless of its spelling (a frog, a university, a euphemism). The form an is used before a word beginning with a vowel sound (an orange, an hour). · An was once a common variant before words beginning with h in which the first syllable was unstressed; thus 18th-century authors wrote either a historical or an historical but a history, not an history. This usage made sense in that people often did not pronounce the initial h in words such as historical and heroic, but by the late 19th century educated speakers usually gave their initial h's a huff, and the practice of writing an before such words began to die out. Nowadays it survives primarily before the word historical. One may also come across it in the phrases an hysterectomy or an hereditary trait. These usages are acceptable in formal writing.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a- 2
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pref.
1. On; in: abed.
2. In the act of: aborning.
3. In the direction of: astern.
4. In a specified state or condition: abuzz.

[Middle English, from Old English, from an, on; see ON.]

Our Living Language Prefixing a- to verb forms ending in -ing, as in a-hunting and a-fishing, was once fairly common in vernacular US speech, particularly in the highland areas of the South and in the Southwest. Such verb forms derive from an Old English construction in which a preposition, usually on, was placed in front of a verbal nouna verb to which -ing had been added to indicate that the action was extended or ongoing. Gradually such prepositions were shortened to a-. The -ing forms came to be regarded as present participles rather than verbal nouns, and the use of a- was extended to genuine present participles. Eventually a- disappeared from many dialects, including Standard English in the United States and Great Britain, although it is still retained today in some isolated dialect areas. Today, speakers who use the a- prefix do not use it randomly. Rather, a- is only used with -ing words that begin with a consonant, have stress on the first syllable, and function as part of a verb phrase, as in She was a-running.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a 3 (ə)
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prep.
In every; to each; per: once a month; one dollar a pound.

[Middle English, from Old English an, in; see ON.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a 4 (ə)
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aux.v.
Informal
Have: He'd a come if he could.

[Middle English, alteration of haven, to have; see HAVE.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a 5
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abbr.
1. acceleration
2. are (measurement)

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
a.
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abbr.
1. acre
2. adjective
3. Latin anno (in the year)
4. Latin annus (year)
5. anode
6. Latin ante (before)
7. anterior

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
A
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abbr.
1. accusative
2. Games ace
3. across
4. adenine
5. alto
6. ampere
7. or Å angstrom
8. answer
9. area
10. Sports assist

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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