a (medicine) Recurring every twenty-four hours or (more generally) daily (of symptoms etc.). (defdate|from 14th c.)
a Happening every day; daily. (defdate|from 15th c.)
a Having the characteristics of something which can be seen, experienced etc. every day or very commonly; commonplace, ordinary; trivial, mundane. (defdate|from 15th c.)
n (medicine|now|_|rare|historical) A fever which recurs every day; quotidian malaria. (defdate|from 14th c.)
n (context|Anglicanism|historical) A daily allowance formerly paid to certain members of the clergy. (defdate|from 16th c.)
n (context|usually with definite article) Commonplace or mundane things regarded as a class. (defdate|from 20th c.)