10 Abbreviations and symbols

10.4 The indefinite article with abbreviations

The choice between a and an before an abbreviation depends on pronunciation, not spelling. Use a before abbreviations beginning with a consonant sound, including an aspirated h and a vowel pronounced with the sound of w or y:

a BA degree

a KLM flight

a BBC announcer

a YMCA bed

a U-boat captain

a UNICEF card

Use an before abbreviations beginning with a vowel sound, including unaspirated h:

an MCC ruling

an FA cup match


an IOU

an MP

an RAC badge

an SOS signal

an NHS hospital

This distinction assumes the reader will pronounce the sounds of the letters, rather than the words they stand for (a Football Association cup match, a high-definition television). MS for manuscript is normally pronounced as the full word, manuscript, and so takes a; MS for multiple sclerosis is often pronounced em-ess, and so takes an. ‘R.’ for rabbi is pronounced as rabbi (‘a R. Shimon wrote’).

The difference between sounding and spelling letters is equally important when choosing the article for abbreviations that are acronyms and for those that are not: a NASA launch but an MC’s toast.

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New Hart's Rules


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