What is the difference between いくつか and 一部?

Question

Both words can translate to "some" or "a few". I understand that both of them are used for countables. So i was wondering if there is an actual difference in their usage or if they are kind of interchangeable. I was told something like:

• いくつか: A small number of something (ex: いくつかのリンゴを買った。I bought a few apples)
• 一部: Some of something (as in: some but not all) (ex: 一部の人々は日本がすべて一番だと思っている。Some people think that Japan is the best at everything. The ratio of people could be anything from like 10% to 90% but it's not everyone.)

But I saw on forums people saying they can be used interchangeably. Is there a difference between these words (in actual definition or in usage)? Thank you in advance!

Answer 1

I think your understanding is correct. いくつかの and 一部の are different, and the difference is as follows:

• いくつかのリンゴを買った。
  I bought some apples.
• 一部のリンゴを買った。
  I bought a part of the apples.
  I bought some of the apples.
  _{(I bought some apples from a specified, larger set of apples.)}

So 一部 is used in contrast to 全部 (all); when you say 一部のX, saying 全部のX ("all of the X") also has to make sense. Saying 一部のリンゴを買った without prior context would sound sudden and confusing, but you can say it after saying something like この店では20個のリンゴを売っている.

Likewise, the expression 一部の人 ("some of the people") is valid only when it's clear who is being referred to when saying 全員 or 全部の人 ("everyone") in the same context. In your example, 一部の人 would be understood naturally as a "part" of all the people in a specific country.