Page 121 - Advanced English Grammar in Use

A / a n a n d o n e

I We use a before words that begin with a consonant sound. Some words start with a vowel letter
but begin with a consonant sound, so we use a before these words, too:
• a university (lo ju:n.../) a European (/a juar.../) a one-parent family (/a WAII.../)
We use an before words that begin with a vowel sound:
• an orange an Italian an umbrella
These include words that begin with a silent letter 'h':
• an hour an honest child
an honour an heir (= a person who inherits money etc., when someone dies)
rtand abbreviations said as individual letters that begin with A, E, F, H, I, L, M, N, O, R, S or X:
• • an MP (Ion em pi:/) an FBI agent (/an ef bi: ai.../) an IOU (/an ai ao jo:/)
But compare abbreviations said as words:
• a NATO general (lo neitau.../) a FIFA official (/a fi:fa.../)

D We can use a/an before singular countable nouns (see also Unit 50).
Sometimes we can use either a/an or one:
• We'll be in Australia for one (or a) year.
• Wait here for one (or a) minute, and I'll be with you.
• She scored one (or a) hundred and eighty points.
Using one in sentences like these gives a little more emphasis to the number.
However, we use one rather than a/an if we want to emphasise that we are talking about only
one thing or person rather than two or more:
• Do you want one sandwich or two?
• Are you staying just one night?
• I just took one look at her and she started crying.
We use one, not a/an in the pattern one...other / another:
• Close one eye, and then the other.
• Bees carry pollen from one plant to another.
We also use one in phrases such as one day, one evening, one spring, etc., to mean a particular,
but unspecified day, evening, spring, etc.:
• Hope to see you again one day. • One evening, while he was working late at the office ...

' We don't use one when we mean 'any one of a particular type of thing':
• I really need a cup of coffee, (not... one cup of coffee.)
• You can never find a paper clip in this office, (not ...one paper clip)
We also use a/an, not one, in number and quantity expressions such as:
fy • three times a year half an hour a quarter of an hour a day or so (= about a day)
• • 50 pence a (= each) litre (notice we can also say '...for one litre')
• a week or two (= somewhere between one and two weeks; notice we can also say 'one or
two weeks')
• a few a little a huge number of...
We use a rather than one in the pattern a...of... with possessives, as in:
• She's a colleague of mine.
• That's a friend of Bill's.

Articles = One and ones