2a or an 
/ə, ˈeɪ/ /ən, ˈæn/ indefinite article
/ə, ˈeɪ/ /ən, ˈæn/ indefinite article ◊A is used before a consonant sound.
▪ a door ▪ a human An is used before a vowel sound. ▪ an icicle ▪ an honor Note that when a word begins with a vowel letter but is pronounced with a consonant sound, a is used. ▪ a one ▪ a union When an abbreviation begins with a consonant letter but is pronounced with a vowel sound, an is used. ▪ an FBI investigation ▪ an LCD display When a word begins with h but the first syllable of the word is not given primary stress, both a and an are used. ▪ a historic ▪ an historic 1 — used before singular nouns when the person or thing is being mentioned for the first time ▪ There was a tree in the field. ▪ A man walked past him. ▪ I heard a shout. ▪ He bought a house, but this is not the house he bought. ▪ I ordered an apple and some cheese: I ate the apple but not the cheese. 2 a — used like one before number words like hundred, thousand, etc. ▪ a hundred and twenty people ▪ a million dollars ▪ a dozen doughnuts
b — used like one before number words like third, fortieth, etc. ▪ This is a [=one] third the size of that.
c — 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
d : one single : even one — used 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.” 3 — used before a word or phrase that indicates a type or class of person or thing ▪ My uncle is a plumber. ▪ Copper is a metal. ▪ She's a very nice lady. — often used before noncount nouns that are modified by an adjective or phrase ▪ a torrential rain ▪ She has a warmth that puts people at ease. ▪ I've always had a fondness for chocolate. 4 — 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] 5 — 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. 6 a — 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.
b — 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. 7 a — 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.
b — used before a family name to show that someone is a member of that family ▪ Did you know that she's a Kennedy? 8 — 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. 9 — used with words like bit and little to form phrases that describe quantity, amount, or degree ▪ She felt a bit tired. ▪ 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.
▪ a door ▪ a human An is used before a vowel sound. ▪ an icicle ▪ an honor Note that when a word begins with a vowel letter but is pronounced with a consonant sound, a is used. ▪ a one ▪ a union When an abbreviation begins with a consonant letter but is pronounced with a vowel sound, an is used. ▪ an FBI investigation ▪ an LCD display When a word begins with h but the first syllable of the word is not given primary stress, both a and an are used. ▪ a historic ▪ an historic 1 — used before singular nouns when the person or thing is being mentioned for the first time ▪ There was a tree in the field. ▪ A man walked past him. ▪ I heard a shout. ▪ He bought a house, but this is not the house he bought. ▪ I ordered an apple and some cheese: I ate the apple but not the cheese.
b — used like one before number words like third, fortieth, etc. ▪ This is a [=one] third the size of that.
c — 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
d : one single : even one — used 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.”
b — 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.
b — used before a family name to show that someone is a member of that family ▪ Did you know that she's a Kennedy?
