I seem to have trouble deciding whether or not to use 'a' or 'an' when followed by quantities:

Built (a/an) 120 lb. robot.


Built (a/an) 18"x 18"x 18" robot.

In terms of pronunciation, the first case could go like:

Built a one-hundred-and-twenty pound robot.

or, like:

Built an a-hundred-and-twenty pound robot.

Which would it be?


1 Answer 1


As usual with the indefinite articles a and an, it depends on the pronunciation of the next word.

I would read your example as: "a hundred-and-twenty pound robot", but "a one-hundred-and-twenty pound robot" would be equally valid.

On the other hand "an a hundred-and-twenty pound robot" would be just wrong. You can't have "an a" together like that.

In your second example, because "eighteen" starts with a vowel sound, it would be "an eighteen-inch by eighteen-inch by eighteen-inch robot".

  • So what would you use with "eight hundred and twenty-seven"?
    – Hot Licks
    Jun 7, 2016 at 12:02
  • @HotLicks you're absolutely right; as the only number which starts with a vowel, eight would need an. I've updated my answer accordingly.
    – Caesar
    Jun 7, 2016 at 13:11
  • "Eight" starts with a vowel sound.
    – Hot Licks
    Jun 7, 2016 at 13:12
  • 'eleven' also starts with a vowel sound. Jun 7, 2016 at 13:27
  • @Caesar Also "11" - an eleven-inch gap.
    – TrevorD
    Jun 7, 2016 at 13:28

Not the answer you're looking for? Browse other questions tagged or ask your own question.