My cumulative list of “words commonly confused” continues with 10 that begin with the letters Q and R. The confusion relates to spelling or meaning.
Traditionally, quote is a verb and quotation is a noun:
May I quote you on that? (verb)
I used a quotation from Dr. Johnson as an epigraph. (noun)
The Chicago Manual of Style includes a note on these words in the “Good usage versus common usage section,” apparently preferring to preserve the distinction in formal writing.
The CMS note also suggests that a difference may exist in the minds of some writers between quote as a noun and quotation as a noun:
quotes: contemporary remarks usable in their writing.
quotations: wisdom of the ages expressed pithily.
This is a spelling problem for speakers who aren’t in the habit of looking closely at words.
Quiet functions as noun, adjective and verb:
In the old days, librarians insisted on absolute quiet from the patrons. (noun)
Parents often worry when their children are excessively quiet. (adjective)