federal
See capitalization, government bodies.
fewer, less
In general use "fewer" for individual items, "less" for bulk or quantity: I had less than $50 in my pocket. But: I had fewer than 50 $1 bills in my pocket.
field house
Two words unless referring to the university’s Memorial Fieldhouse.
figuratively, literally
"Figuratively" means in an analogous sense, but not in the exact sense: He scared her to death. "Literally" means in an exact sense. Do not use it figuratively: Grammar literally makes my head explode.
flier, flyer
"Flier" is the preferred term for an aviator or a handbill. "Flyer" is the proper name of some trains and buses: The Western Flyer.
follow up (v.), follow-up (n. and adj.)
former
Always lowercase. But retain capitalization for a formal title used immediately before a name: former President Nixon.
fractions
Spell out amounts less than one in stories, using hyphens between the words: two-thirds, four-fifths, seven-sixteenths, etc. Use figures for precise amounts larger than one, converting to decimals whenever practical.
full time, full-time
Hyphenate only when used as a compound modifier: He works full time. She has a full-time job.