epistle
Concise Oxford English Dictionary © 2008 Oxford University Press:
epistle /ɪˈpɪs(ə)l/
▶noun formal or humorous a letter.
■ (Epistle) a book of the New Testament in the form of a letter from an Apostle.
– origin OE, via L. from Gk epistolē, from epistellein ‘send news’.
'epistle' also found in these Oxford entries:

