Example: a phone, a car, a motorbike, a train, a school, a building, a hotel, a restaurant…etc.
NOTE: Some words start with a vowel letter but begin with a consonant sound, so we use “a” before these words, too.
Example: a university, a Europe, a one-parent family…etc.
2) AN: We use “an” before words that begin with vowel sound.
Example: an orange, an apple, an egg, an Italy, an umbrella, an axe…etc.
NOTE 1: Some words start with a consonant but begin with a silent sound, so we use “an” before these words as well. These kinds of word always start with letter “h”.
Example: an hour, an honest personnel, an honor, an heir…etc.
NOTE 2: We use “an” before abbreviations said as individual letters that begin with “A, E, F, H, I, L, M, N, OK, R, S, or X”
Example: an MP, an IMF, an FBI agent, an IOU, an HRU…etc.
NOTE 3: We use “a” not “an” before abbreviations said as words.
Example: a NATO general, a FIFA official, a UNECIEF member…etc.
3) ONE
a- We use “one” rather than “a/an” if we want to emphasize that we are talking about only one thing or person rather than two or more.
Example:
- Do you have one sandwich or two?
- Are you staying just one night?
- I just took one at her and she started crying.
b- We use “one” in the pattern one…other / another.
Example:
- Close one eye, and then the other.
- Bees carry pollen from one plant to another.
c- We use “one” in phrases such as one day, one evening, one spring…etc., to mean a particular, but unspecified day, evening, spring…etc.
Example:
- Hope to see again one day.
- One evening, while he was working late at the office.
NOTE 1: We don’t use “one” when we mean ‘any one of a particular type of thing’.
Example:
- I really need a cup of coffee.
- You can never find a paper clip in this office.
NOTE 2: We also use “a/an”, not “one” in number and quantity expression such as:
- three times a year, half an hour, a quarter of an hour, a day or so (= about a day)
- 50 pence a liter (notice we can also say ‘…for one liter’)
- a week or two (notice we can also say ‘…one or two weeks’)
- a few, a little, a huge number of…
NOTE 3: We use “a” rather than “one” in the pattern “a…of…” with possessives.
Example:
- She’s a colleague of mine.
- That’s a friend of Bill’s.
- It’s a product of Sony Company’s.
