Use small letters and periods for most abbreviations of Latin terms. Common Latin expression like those listed here are not normally underlined or italicized. They are usually used in bibliographies, footnotes, lists, and references.

In standard writing, use the English equivalent or write out the whole word.

They are usually underlined or italicized in formal references, notes, and bibliographies.

Abbreviation Equivalent
c., ca. circa, about, around
e.g. for example
et al. et alii, and the others
etc. et cetera and so on, note the spelling
et seq. and the following (usually pages)
f. and the next page
ff. and the following pages
i.e. id est, that is
N.B. Nota Bene, note well (capitalize)
op. opus, work (of art)
q.v. which see
v. see
v., vs. versus
viz. vidilicet, namely

Correct: Geoffrey Chaucer (c. 1343-1399)
Incorrect: Geoffrey Chaucer was born c. 1343.
(Standard sentence, not a reference–write out the word or use the English equivalent.)

Correct: Geoffrey Chaucer was born circa 1343.

Correct: Geoffrey Chaucer was born about 1343.