American English -- Compound Nouns -- Page 3

Explanation and Discussion In American English Compound Nouns are sometimes hyphenated and sometimes not. No real rules exist but some trends do. Below I have some of the major groups of words and their generalities.

On Words Compound nouns ending in "on" are typically hyphenated. For Example:
add-on carrying-on come-on follow-on goings-on hangers-on lookers-on put-on run-on slip-on turn-on


However with this exception
carryon


Off Words Compound nouns ending in "off" are either solid or hyphenated. For example:
checkoff cutoff falloff kickoff knockoff layoff leadoff liftoff payoff runoff
shutoff standoff takeoff turnoff brush-off drop-off goof-off play-off rake-off rip-off
sell-off send-off show-off sign-off spin-off tip-off trade-off write-off