A&d là thuốc gì

◊ A is used before a consonant sound.

An is used before a vowel sound.

Note that when a word begins with a vowel letter but is pronounced with a consonant sound, a is used.

When an abbreviation begins with a consonant letter but is pronounced with a vowel sound, an is used.

When a word begins with h but the first syllable of the word is not given primary stress, both a and an are used.

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

  • a hundred and twenty people

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

  • This is a [=one] third the size of that.

used like one before units of weight, measurement, etc.

  • a pound or two [=one or two pounds]

  • a week or two [=one or two weeks]

  • a foot and a half of water = one and a half feet of water

: one single : even oneused in negative constructions

  • They didn't charge me a penny. [=they didn't charge me anything at all]

  • “Did she say anything about it?” “Not a word.”

used before a word or phrase that indicates a type or class of person or thingoften used before noncount nouns that are modified by an adjective or phrase

  • She has a warmth that puts people at ease.

  • I've always had a fondness for chocolate.

used like any to refer in a general way to people or things

  • A person who is sick can't work well. [=people can't work well if they are sick]

used before a proper noun to indicate limited knowledge about the person or thing being mentioned

  • A Mr. Smith [=a man named Mr. Smith] called to ask about the job.

  • Among the towns of the area there is a Newton, I believe.

used before a proper noun that is acting as an example or type

  • the attractions of a Boston or a Cleveland

  • His friends say he's an Einstein in regard to science.

used before the name of a day of the week to refer to one occurrence of it

  • My birthday falls on a Tuesday this year.

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

  • The museum recently purchased a Rembrandt. [=a painting by Rembrandt]

  • My violin is a Stradivarius.

used before a family name to show that someone is a member of that family

  • Did you know that she's a Kennedy?

used before a proper noun referring to a person or thing that has a particular quality

  • A triumphant Ms. Jones greeted her supporters. [=Ms. Jones was triumphant when she greeted her supporters]

  • We were met at the door by an embarrassed Mr. Brown. [=Mr. Brown was embarrassed when he met us at the door]

  • We had a very mild January.

used with words like bit and little to form phrases that describe quantity, amount, or degree

  • It's getting a little late.

10 

used in phrases that describe how often something occurs, how fast something is going, etc.

  • They meet twice a week. [=twice each week]

  • The car was traveling at a hundred miles an [=per] hour.

[ uh; when stressed ey ]

/ ə; when stressed eɪ /

See synonyms for a on Thesaurus.com

not any particular or certain one of a class or group: a man; a chemical; a house.

a certain; a particular: one at a time; two of a kind; A Miss Johnson called.

another; one typically resembling: a Cicero in eloquence; a Jonah.

one [used before plural nouns that are preceded by a quantifier singular in form]: a hundred men [compare hundreds of men]; a dozen times [compare dozens of times].

indefinitely or nonspecifically [used with adjectives expressing number]: a great many years; a few stars.

one [used before a noun expressing quantity]: a yard of ribbon; a score of times.

any; a single: not a one.

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1

First recorded in 1200–50; Middle English; originally preconsonantal phonetic variant of an1

In both spoken and written English the choice of a1 or an1 is determined by the initial sound of the word that follows. Before a consonant sound, a is used; before a vowel sound, an : a book, a rose; an apple, an opera. Problems arise occasionally when the following word begins with a vowel letter but actually starts with a consonant sound, or vice versa. Some words beginning with the vowel letter u and all words beginning with the vowel letters eu are pronounced with a beginning consonant sound, as if the first letter were y : a union; a European. Some other spellings that begin with a vowel letter may also stand for an initial consonant sound: a ewe; a ewer. The words one and once and all compounds of which they are the first element begin with a w sound: a one-room apartment; a once-famous actor.
The names of the consonant letters f, h, l, m, n, r, s, and x are pronounced with a beginning vowel sound. When these letters are used as words or to form words, they are preceded by an : to rent an L-shaped studio; to fly an SST. The names of the vowel letter u and the semivowel letters w and y are pronounced with a beginning consonant sound. When used as words, they are preceded by a : a U-turn; The plumber installed a Y in the line.
In some words beginning with the letter h, the h is not pronounced; the words actually begin with a vowel sound: an hour; an honor. When the h is strongly pronounced, as in a stressed syllable at the beginning of a word, it is preceded by a : a history of the Sioux; a hero sandwich. [In former times an was used before strongly pronounced h in a stressed first syllable: an hundred. ] Such adjectives as historic, historical, heroic, and habitual, which begin with an unstressed syllable and often with a silent or weakly pronounced h, are commonly preceded by an, especially in British English. But the use of a rather than an is widespread in both speech and writing: a historical novel; a habitual criminal. Hotel and unique are occasionally preceded by an, but this use is increasingly old-fashioned. Although in some dialects an has yielded to a in all cases, edited writing reflects usage as described above.

7-dehydrocholesterol, “800” number, 8d, 900 number, 911, a, A1, A1c, A2, A2 level, A3

[ uh; when stressed ey ]

/ ə; when stressed eɪ /

each; every; per: ten cents a sheet; three times a day.

2

Originally Middle English a, preconsonantal variant of on [see a-1]; confused with a1

Informal. a reduced, unstressed form of of [often written as part of a single, unhyphenated word]: cloth a gold; time a day; kinda; sorta.

3

Middle English; unstressed preconsonantal variant of of1

a reduced, unstressed form of auxiliary have following some modals, as might, should, could, would, and must [usually written as part of a single, unhyphenated word]: We shoulda gone.

4

First recorded in 1300–50; Middle English; a phonetic variant of have

/ ə, æ, ɑ /

5

First recorded in 1200–50; Middle English a, ha

abbreviation Measurements.

/ ɑ, ɔ /

/ eɪ /

noun, plural A's or As, a's or as.

the first letter of the English alphabet, a vowel.

any spoken sound represented by the letter A or a, as in bake, hat, father, or small.

something having the shape of an A.

a written or printed representation of the letter A or a.

a device, as a printer's type, for reproducing the letter A or a.

Electricity. ampere; amperes.

Physics. angstrom; angstroms.

British. arterial [used with a road number to designate a major highway]: Take the A525 to Ruthin.

the first in order or in a series.

Sometimes a .

  1. [in some grading systems] a grade or mark, as in school or college, indicating the quality of a student's work as excellent or superior.
  2. [in some school systems] a symbol designating the first semester of a school year.

Music.

  1. the sixth tone in the scale of C major or the first tone in the relative minor scale, A minor.
  2. a string, key, or pipe tuned to this tone.
  3. a written or printed note representing this tone.
  4. [in the fixed system of solmization] the sixth tone of the scale of C major, called la.
  5. the tonality having A as the tonic note.

Physiology. a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group A or AB and to receive blood from persons of O or A.Compare ABO system.

Sometimes a . the medieval Roman numeral for 50 or 500.Compare Roman numerals.

Chemistry. [formerly] argon.

Chemistry, Physics. mass number.

Biochemistry.

Also a .Logic. universal affirmative.

a proportional shoe width size, narrower than B and wider than AA.

a proportional brassiere cup size, smaller than B and larger than AA.

a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.

a reduced form of the Old English preposition on, meaning “on,” “in,” “into,” “to,” “toward,” preserved before a noun in a prepositional phrase, forming a predicate adjective or an adverbial element [afoot; abed; ashore; aside; away], or before an adjective [afar; aloud; alow], as a moribund prefix with a verb [acknowledge], and in archaic and dialectal use before a present participle in -ing [set the bells aringing]; and added to a verb stem with the force of a present participle [ablaze; agape; aglow; astride; and originally, awry].

1

Middle English, late Old English; cf. a2, nowadays

a reduced form of the Old English preposition of: akin; afresh; anew.

an old point-action prefix, not referring to an act as a whole, but only to the beginning or end: She arose [rose up]. They abided by their beliefs [remained faithful to the end].

3

Middle English; Old English a- [unstressed], ǣ-, ā-, ō- [stressed; see abb, woof1, oakum], rarely or- [see ordeal], ultimately from unattested Germanic uz- from unstressed Indo-European uss-, from ud-s [these latter two also unattested], akin to out; in some cases confused with a-4, as in abridge

variant of ab- before p and v: aperient; avert.

4

Middle English

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