Should I use "half the time" or "half of the time"? [closed]

If I wanted to say that someone finished in 30 minutes when they had one hour to complete a given task, should I say "he did it in half the time" or "he did it in half of the time"?

The difference is whether the word "half" is used as a noun or an adjective. Half is a noun in "half of the time" and an adjective in "half the time", modifying "time". Because both are gramatical, the only way to chose is because of meter and voice. In Hemmingway-style American terseness, which is what I was taught in school, words that can be omitted should be. "Of" adds nothing in meaning, but takes up a syllable, so for writing for newspapers or radio, leave it out. If writing poetry, go for it if it improves your voice. If using it in fictional prose, it depends on if your character is formal or informal in voice. My grandmother would never have used "in half the time", because of her naturally grandiose voice. She believed that if something could be said slowly, it should be. But then she was an upstate New Yorker who had moved to Alabama as a teen and married into old money (alas now gone).

So, in short, if you are Faulkner, use "of", if Hemmingway, don't. There is no idiom that means maybe-maybe not, because that's just what the words mean. Idioms are for non-litteral use of words. E.g., like teats on a boar hog. People who are unfamiliar with farms still know the phrase, at least in certain parts of the US. Others need it explained. No one needs "half the time" explained to them, unless they are foreign, and then the words themselves can explain it, unlike teats on a boar hog.

Then there's the use of "half time" as a compound adjective, as in "the half-time performance of the marching band", which is never "half-of-time", but is frequently "halftime", especially when used as a noun, as in, "We'll be right back with halftime after a few words from our sponsor."

I'm inclined to say that "half of the time" is old-fashioned. Language gets shorter, not longer over time. "Gigantic and enormous" is now just ginormous. (This happened in the 1940s).

-- Max Crane.