いちぶぶん一部分ichibubun
1.

A small or limited segment that comprises a fraction of a larger whole, often used to refer to something that is not entirely visible or comprehensible.

2.

A specific section within a complete entity, highlighting its status as a subset that may carry distinct characteristics compared to the entirety.

3.

A minor component of a whole, underscoring its incomplete nature or the idea that only a fraction of something is being considered or used.

Example:

その建物の一部分だけが地震で破壊された。