It depends on the context that it is used. Strictly speaking it means total population divided by three = one third of the population. But ... if you said something like "a third of people who were asked about it said that learning English was difficult" :-) ... then it would mean one person out of each three who were asked. Hope that makes it a bit clearer.

1/3, so one out of three people.

Hlw susan, Your answer is confusing. :(

One out of thee people but that could be ⅓ of population or ⅓ of the sample asked. Parameters would have to be defined. e.g. One third of Cook county believes...... One third of the US believes.... OR One third of respondents believe....... Susan