문어(mun-eo, muneo)
Refers to formal, stiff writing style or written language (literary style).
When to use
formal documents, academic papers, newspaper articles
The nuance
문어 is used mainly in formal documents, academic papers, newspapers; inappropriate for casual speech or friendly writing.
글(geul)
A general term for writing, text, or letters, covering all types of written content.
When to use
diaries, letters, blogs, casual writing
The nuance
글 is the broadest term, referring to any kind of writing including casual notes, diaries, letters, blogs.
책말(chaek-mal, chaekmal)
Refers to formal, literary expressions used specifically in books or official documents.
When to use
books, academic papers, reports
The nuance
책말 is used mainly in books, papers, reports with literary style to give a formal tone; unsuitable for everyday writing.