hyphen

B. Hyphens are also used within the word to connect a prefix or suffix to the stem. With most prefixes and suffixes it is normal to write the whole compound as a single word; the use of the hyphen is exceptional, and the writing of prefix or suffix and stem as two words virtually unknown.

The hyphen is used in the following cases:

1. After a number of prefixes that are considered to be living formative elements, i.e. prefixes that can be freely used to form new compounds: ex- (=formerly), e.g. ex-President; neo- (denoting a revived movement), e.g. neo-Nazism; non-, e.g. non-stick; pro- (=in favour of), e.g. pro-marketeer; self-, e.g. self-destructive. Exceptions: Neoplatonism (-ic, etc.); selfsame, unselfconscious.
2. After a number of prefixes to aid recognition of the second element, e.g.: anti-g,
or to distinguish the compound from another word identically spelt, e.g.: un-ionized (as against unionized).
3. Between a prefix ending with a vowel and a stem beginning with the same vowel, e.g.: de-escalate, pre-empt.
4. Between a prefix and a stem beginning with a capital letter, e.g.: anti-Darwinian, hyper-Calvinism, Pre-Raphaelite.
5. With some living suffixes forming specially coined compounds, e.g.: Mickey Mouse-like;
or still regarded to some extent as full words, such as -wise (= as regards —), e.g.: Weather-wise we have had a good summer.
6. With suffixes in irregularly formed compounds, e.g.: unget-at-able.
7. With the suffix -like after a stem ending in -l, e.g. eel-like, when attached to a word of two or more syllables, e.g.: cabbage-like,
and with the suffix -less after a stem ending in double -l, e.g.: bell-less, will-lessness.

Note. In American spelling there is a greater tendency than in British spelling to write compounds as one word, rather than hyphened, e.g.

nonplaying, nonprofit, roundhouse, runback, sandlot.

Hyphens between words