- 권 (卷)권 (卷)[Dictionary definition #1]: a unit of amount of books.
- 부 (部)[Dictionary definition #2]: a unit of amount of books and newspapers.
- 편 (篇)[Dictionary definition #2]: a unit of amount of pieces, such as books, poetry, and movies.
- 편 (篇)[Dictionary definition #1]: a unit of amount of books forming part of a work or series; i.e. volumes.
- 호 (號)[Dictionary definition #3]: a unit of .......
- 편 (篇)[Dictionary definition #3]: a unit of .......
- 장 (章)장 (章)[Dictionary definition #1 and #2] or 가름[Synonym]: chapter.
- 절 (節)절 (節)[Dictionary definition #1]: paragraph.
- 낱말단어 (單語) or 단어 낱말: word.
- 마디 or 소절 (單語小節)
- 글자 (글字) or 자 (字): wordletter; or, a unit of number of letters.
memo (editing)
- 소절
- 자 (字): letter.
The reason why they're mostly one-letter words is maybe because they're almost unit words.