The English indefinite articles are a and an. They refer to something unspecific. Here are example sentences.
|I bought a car|
|She saw an elephant.|
|They have an idea.|
|Do you have a pen?|
In general, the indefinite article a is used in front of nouns and adjectives that begin with a consonant. The indefinite article an is used in front of nouns and adjectives that begin with a vowel. However, there are a few exceptions. Nouns and adjectives that begin with eu– require the indefinite article a.
|a European country|
|a eucalyptus tree|
The same rule applies to nouns that begin with ur-.
|a uranium mine|
Most nouns or adjectives that begin with uni– also require the indefinite article a.
|a unit of measure|
Be careful, there are some adjectives that begin with uni– which follow the general rule.
|an unidentified flying object|
|an unimportant call|
|an unintended result|
|an unintelligent person|
Note that the sound produced by eu-, ur-, and uni– is a –y sound. Because these words do not begin with a pure vowel sound the indefinite artcle a is used.
In the examples below, notice that the letter H has two forms. The aspirated form requires an expulsion of air. The unaspirated form is completely silent which means there is no expulsion of air so the letter H contributes no sound to the spoken word. It is as if the H does not exist. Therefore, the noun requires the indefinite article an.
|aspirated H||unaspirated H|
|a hat||an hour|
|a helicopter||an honest man|
|a house||an honor|
|a human||an herb|
Note that the unaspirated H is almost always followed by the letter O, with one one exception. In American English, the noun herb also has an unaspirated H, but in British English, herb is pronounced with an aspirated H.
The unaspirated H is extremely rare in English. The four examples above (hour, honest, honor, herb) and their variations (honestly, honorable, herbalist, etc.) represent all the words in English that use an unaspirated H.
Test your knowledge: Quiz – Indefinite Articles