What are the rules for English word formations?
An overview of some rules for word formation in English is offered below.
Frequent collocations over time and with usage become double- or triple-word compounds that with further time and usage become hyphenated compounds that with further time and usage become single-word compounds.
Usually the first syllable of the lead word and all or most of the second word are used for forming words though blending, like electronic mail blended to the blend compound e-mail, which is rapidly becoming a single-word blend compound email.
Back formations are formed by removing a morpheme incorrectly perceived as a derivative suffix to create a new word, as in the removal of -ar from burglar to form burgle or the removal of -or from editor to form edit
The most common combining forms are Greek or Latin, which are derived from nouns or adjectives or verbs, that combine with other combining forms.
Derivational prefixes rarely change word class and often indicate negation (e.g., un-, in-, non-) or relationship (e.g., im-, pre-).
Derivational suffixes are used within careful guidelines and often change word class. Some examples are:
-ism, used on Greek loanword verbs to form action nouns (e.g., realism).
-able, a Latin suffix with the meaning of "capable of, tending to, etc", appears on Latin loanwords (e.g., laudable) and on other words in English (e.g., teachable) and is adjective forming.
-ation, a combination of Latin suffixes -ate and -ion, is used to forms nouns from stems ending in -ate (e.g., separate) and on other English words (e.g., starve).
-ness, an original English suffix, from Old English and Middle English -nes, that forms abstract nouns (e.g., goodness) from adjectives and participles.
Some other suffixes are -ful, -fy, -ify, -ise or -ize, -ist, -ity, -ly, and -ment. A good dictionary will provide the specifics of etymology (origin), usage and word class changes. Good online dictionary sources are Cambridge Dictionaries Online and Dictionary.com.