THE INDEFINITE ARTICLE RULES
This article is about the correct usage of the indefinite articles ‘an’ and ‘a’.
A common grammar misconception is that the article ‘an’ is used before words that begin with a vowel (a, e, i, o, u), while the article ‘a’ is used before all words that start with a consonant (non-vowels). In reality, the usage of the articles ‘an’ and ‘a’ are dependant more on the first sound of the word rather than its spelling.
WHEN TO USE ‘AN’
The words that start with a vowel sound, like ‘honest’ or ‘honorable’, should have ‘an’ before them.
Examples: an hour late, an honest person, an heir to the throne, an honorable idea.
Even though these words begin with ‘h’, a consonant, when you pronounce them, the ‘h’ is silent. The first sound of the word is the vowel sound ‘o’. Hence, these words take the article ‘an’ before them.
Other general examples are: an egg, an owl, an old woman, an idea, an oily residue, an umbrella, an unbearable burden.
The article ‘an’ should always be used before words that start with vowel sounds.
So, you need to remember that if a word begins with a consonant, but has an initial vowel sound, (‘honest’ as an example), use the article ‘an’ before it.
WHEN TO USE ‘A’
In words such as unique, university, unicycle or user, even though the first alphabet is a vowel, the sound produced is ‘yoo’. ‘Y’ is a consonant and hence words that sound like they start with ’Y’, take the article ‘a’ before them.
Examples are: a united front, a U-tube, a European city, a university, a unicycle, a user.
Similarly, in the word x-ray, the ‘ex’ is the starting sound hence the article ‘an’ goes before it. ‘One-month offer’ starts with a consonant ‘w’ and is written as ‘a one-month offer’.
Other general examples: a baby, a picture, a story, a cup, a bottle, a door, a phone, a comma.
The article ‘a’ should always be used before words that start with consonant sounds.
So, you need to remember that if a word begins with a vowel, but has an initial consonant sound, (‘university’ as an example), use the article ‘a’ before it.
While using an article with abbreviations, it gets a little tricky. The first thing to do is to figure out if the abbreviation is an acronym (pronounced as one word) or letter-by-letter. For example, HIV is pronounced ‘aych-eye-vee’ but the acronym AIDS is pronounced as one word. Then, depending on the initial sound of their pronunciation, appropriate articles can be used.
It would be right to say ‘a Masters in Business Administration’. But, if you were using the abbreviation, it would be ‘an MBA’, as the abbreviation is pronounced as ‘em-bee-ay’.
Other examples: an NGO, an HIV patient, an NBC reporter, an NBA coach, an SOS, a US senator, a UN mission
Some abbreviations like ‘HEPA filter’ do not use the article ‘an’, as HEPA is an acronym that starts with a consonant sound.
SUMMARY OF THE RULES:
Rule 1: The article ‘a’ is used before a consonant sound; the article ‘an’ is used before a vowel sound.
Rule 2: Before a letter, an abbreviation, an acronym or a numeral, ‘a’ or ‘an’ is used according to the way, the letter or numeral is pronounced.
For some words like historic, hotel, heroic, ‘a’ and ‘an’ can both be used in writing (an historic, a historic). In the past, these words were pronounced with a silent ‘h’. The article ‘an’ was therefore used before them. But, nowadays the language has evolved to pronounce the ‘h’ in many of these words. Words like heir, hour, and honest, in general have silent ‘h’. Other words, like herb or humble are sometimes pronounced both ways. The articles used with such words in transition depend on personal choice of pronunciation.