What is the difference between these two sentences:
I’m one hundred percent sure.
I’m a hundred percent sure.
For me the only difference between the two sentences is that the second sentence is more formal.
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.
Sign up to join this communityWhat is the difference between these two sentences:
I’m one hundred percent sure.
I’m a hundred percent sure.
For me the only difference between the two sentences is that the second sentence is more formal.
The two phrases have the same basic meaning, but native speakers tend to use the "one hundred percent sure" wording in order to to give a greater impression of certainty. In speech, you can emphasise the word "one" more strongly than "a" and the phrase is spoken with a regular rhythm as ONE HUNdred perCENT SURE.
There is no difference. However, I have heard the former more frequently. Maybe, in India though.
OALD defines it:
a/one hundred percent - in every way.
“One hundred percent” is more emphatic. When spoken, the stress naturally falls on “one”. But other than that, they are completely equivalent. A similar emphasis can be achieved with “a hundred percent” by stressing the quantity “hundred”.
Note the examples given in Oxford Learners Dictionaries:
The statement about having family support is stronger than the other two.
“I still don't feel one hundred percent” is not incorrect, but feels more awkward when spoken. A native speaker would more likely use “a hundred” here, as in the dictionary example. Perhaps “don't feel a hundred percent (well)” means “don't feel quite well”; but “don't feel one hundred percent” or “don't feel a hundred percent” mean “don't feel completely well”?
“Not 100% sure” is an interesting case. Because of the negation, you would normally use the softer “a hundred” form. To me, “I'm not a hundred percent sure” means “I'm not very sure”; whereas “I'm not one hundred percent sure” means “I'm reasonably sure but not completely certain” (with the spoken stress on the words in italic/oblique font).
This is not a distinction that I see in the affirmative “I am a/one hundred percent sure”. Both mean “completely sure”. It's only a difference in emphasis, not degree.
There's also a third written form that I've slipped in above: “100%”. Here, 100 can be pronounced a hundred or one hundred, and the writer is giving no indication as to which.
[Acknowledgement to Maulik and David, I've drawn on their answers in formulating this one.]
I tend to say “I’m a hundred . . .” but that may be because of my Southern U.S. tendency to slur over certain word landscapes, so to speak.