Understanding the correct usage of indefinite articles and abbreviations can be a challenge for both native and non-native English speakers. Should it be a MRI scan or an MRI scan; a UNESCO heritage site or an UNESCO heritage site? This post first describes the difference between acronyms and initialisms, before explaining the reason why we use an MRI scan, for example, despite the abbreviation beginning with a consonant.
Abbreviations: are they acronyms or initialisms?
The first step to establishing the usage of indefinite articles and abbreviations is to define whether the abbreviation is an acronym or an initialism. These can be best described as follows:
- Acronyms: An acronym is an abbreviation that takes the first letter of each word to create a new word. Common examples would be UNESCO (United Nations Educational, Scientific and Cultural Organization), NASA (National Aeronautics and Space Administration) and NATO (North Atlantic Treaty Organization), where we read the acronym as a complete word.
- Initialisms: An initialism is an abbreviation that takes the first letter of each word to create a new word which is read letter by letter, rather than as one complete word. Common example would be FBI (Federal Bureau of Investigation), URL (Uniform Resource Locator) and BBC (British Broadcasting Corporation), where we read each initialism by their individual letters: F-B-I, U-R-L and B-B-C.
How to be clear on the usage of indefinite articles and abbreviations
When we are engaging with written and spoken English under normal circumstances we know from our elementary linguistic knowledge we use a + word beginning with a consonant (e.g. a piece or research, a laboratory experiment) and an + word beginning with a vowel (e.g. an investigation, an author).
When we are dealing with abbreviations, however, we need to consider the first sound of the acronym or initialism, and not the actual letter. When we review the sounds of the English language the number of vowel sounds increases from 5 letters to 20 vowel sounds (see image below).
- When an abbreviation begins with a vowel sound we use the indefinite article an
- When an abbreviation does not begin with a vowel sound we use the indefinite article a
This is starting to sound complicated
Well yes, and no. While invaluable for pronunciation, learning the phonemic alphabet is both challenging and time consuming. The key to quickly knowing if the initial sound is a vowel or consonant is to use transliteration, that is to read the word aloud. So, for example:
AIDS /eɪds/ – the first sound is a vowel (‘a’ as in hay) and so an AIDS epidemic
NATO /neɪtəʊ/ – the first sound is a consonant (‘n’ as in near) and so a NATO exercise
SARS /sɑːz/ – the first sound is a consonant (‘s’ as in space) and so a SARS outbreak
UNESCO /juːneskəʊ/ – the first sound is a consonant (‘y’ as in yellow) and so a UNSECO site
MRI /em ɑːr aɪ/ – the first sound is a vowel (‘e’ as in end) and so an MRI
CD /siːdiː/ – the first sound is a consonant (‘s’ as in sea) and so a CD cover
FBI /ef biː aɪ/ – the first sound is a vowel (‘e’ as in end) and so an FBI investigation
UN /juː en/ – the first sound is a consonant (‘y’ as in yellow) and so a UN conference