At university I learned the process and some of the details of how to derive new words from old ones using prefixes and suffixes, and how this process makes words change their part of speech, but I know how this works only for the process of translating from English. For example, if I see the word blacken, I know that’s a verb derived from the adjective black, and so on.

Can somebody please explain to me the process of making new words with prefixes and suffixes when it comes to deriving new words in English? I know I can't just add en‑ to the start of just any old adjective and make a brand new verb out of it — or can I? Can I use en‑ to transform any word into a verb, like from light to enlight? Or can I do this only with different groups of words (parts of speech?), and if so, than with which ones?

  • This is probably less of a question for this forum (which is more about English usage), but instead better suited for the English Language Learners one (ell.stackexchange.com) – Oliver Mason Sep 13 '17 at 10:13
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    We've had arguments about wordness and the scope of productivity (how often rules apply) on ELU before. One can't 'make new words' (and expect them to be accepted into the lexis within a few days) at will, no matter how closely to common patterns one operates. One can use candidate words (and even pure gibberish) if one so desires, but a degree of understanding and usage is required for a candidate word to be accepted into the lexis. – Edwin Ashworth Sep 13 '17 at 11:34

As @EdwinAshworth says, one cannot simply make up new words*, or at least one can't expect others to understand the results. English has, over the years, borrowed words and lexical rules from many other languages, resulting in the richly varied and often wildly inconsistent language we have today.

For example, we have at least five** different prefixes meaning "not": "un" ("unlikely"), "im" ("impossible") "a" ("apolitical") "non" ("nonpartisan") and "in" ("independent"). It is not the case that you can stick any of these at the start of any existing word to get a new "valid" word. You would have something that people would have to try to guess the meaning of. Some wouldn't bother, some would get it right, and some would get it wrong. All of them might think you can't speak English.

*Making up new words, or neologisms, does actually happen all the time. It can be fun. Some of them catch on and enter the dictionary. But, all of them tend to cause confusion in the reader or listener, and if your aim is to create a clear communication then you should avoid it.

**this might increase as I keep thinking of others and coming back to edit the question.

EDIT: as @tchrist points out in the comments, the in-, il-, im- and other similar (ie an i followed by a consonant) prefixes are all really attempts to spell the same prefix, which is simple "i-". That is, i'logical becomes "illogical", "i'possible" becomes "impossible", "i'credible" becomes "incredible", etc, simply according to which consonant seems to most naturally fill the gap represented by the apostrophe in my examples above. In other words, if one was to try to say "ih-possible" it's a bit awkward, and we will "pick" a sound to fill the gap, and "im" seems most natural in that case.

  • Be aware that in‑, im‑, il‑, ir‑ are really all the same negatory prefix; the n simply assimilates to the following consonant. – tchrist Sep 13 '17 at 12:55
  • @tchrist do you mean in words like "illogical", that the "l" is there after the i just to help make the word more clearly pronounceable? – Max Williams Sep 13 '17 at 12:56
  • It's because of how assimilation of consonants works in Latin and her daughters, even her step-child like us. Wiktionary observes that “Before certain letters, in‑ becomes: i‑ before gn, e.g. ignoble; il‑ before l, e.g. illegal; im‑ before b, m, or p, e.g. improper; ir‑ before r, e.g. irresistible.” This is the expected and customary regressive assimilation of nasals that always happens in contact with a following consonant whose own point of articulation is at further remove from the nasal’s. – tchrist Sep 13 '17 at 13:01
  • @tchrist, very interesting, thanks. Obviously there are still plenty of others that this doesn't apply to (non-, a-, un- etc) – Max Williams Sep 13 '17 at 13:37

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