When to use hyphens (-)

→Numbers (from twenty-one to ninety-nine) and fractionsThirty-two, forty-eight, fifty-six, sixty-one, seventy-nine, eighty-three etc.
Four-fifths, two-thirds, three-quarters etc.

→PrefixesCo- e.g. co-education, co-pilot
E- e.g. e-mail, e-commerce
Ex – e.g. ex-husband, ex-wife, ex-president
Half- e.g. half-price, half-hour, half-term
Mid- e.g. mid-week, mid-term
Non- e.g. non-profit, non-smoking
Pre- e.g. pre-school
Post- e.g. post-war, post-publication

→Compound nounsbreak-dancing, back-up, bee-keeping, all-rounder, free-for-all, daughter-in-law, chit-chat, double-decker etc.

→Compound adjectives
absent-minded, duty-free, back-breaking, day-to-day, long-distance, mass-market, hot-tempered, off-line etc.

→Compound verbsto lip-sync, to baby-sit, to house-hunt