Surely the most famous new word coated in science fiction is "robot", in the 1920 play by the Czech writer Karel Capek ': RUR ("Rossum's Universal Robots"). I do not know any Czech but I dare say "robot" comes from a root similar to the Russian rabotat , to work. Here, therefore, rather than a word that is completely invented from nothing. we have a new form of an existing word, expressing a new idea.
"Robot" is there before some way along the spectrum that extends from those neologisms which are merely convenient abbreviations (such as "mascon" for "concentratin of mass"), to really new words and ideas. (Of course a writer can also invent a new word to express an old idea, although this is usually rather pointless. I can not be bothered to look it up.)
Even if they are mostly mere abbreviations, new words can offer a new slant on previously expressed ideas.
Perhaps an example of this is "pauk", in Brian Aldiss' Hellliconia Spring . "Pauk" means "trance in which one can commune with the spirits of one's ancestors". Or in which one thinks one can …. for it is not clear, from the Helliconia trilogy as a whole, whether pauk is a genuine phenomenon of soul-contact or whether it is a mental illusion existing at a certain stage of society. The latter interpretation is suggested by the fact that the "spirits" of the departed apparently change in mood, from grumpy to sweet-tempered, as civilization advances.
A vaguer, but possibly more original term, is the Martian word "grok" in Heinlein's Stranger in a Strange Land . If you grok, you are tuning in to some ineffective wholeness; it is a mystical concept, perhaps too vague to be useful, but at least we can say in its favor, that no obvious equivalent previously in the English language.
Turning from the abstract to the concrete, a derivation of an existing word used for a new purpose is "drainer" in Robert Silverberg's A Time of Changes . A drainer is a member of a despised profession, a kind of secular confessor, to who one unburdens oneself verbally in private, in order to rid oneself of stress, in a culture which forbids the open use of the personal pronoun "I".
Jack Vance coined new words for the days of the week in Araminta Station , simply to avoid the jarring incongruity of using our familiar Friday, Saturday, etc, in the context of a far planet tens of thousands of years in the future, even though its residents are human, descended from us and similar to us culturally. He was right to do so. The words he chose are beautiful additions to the atmosphere of his tale.
An interesting example of an author who has carefully eschewed neologism is Gene Wolfe, who in an appendix to the first volume of his far-future epic The Book of the New Sun has stated:
In rendering this book – originally composed in a language that has not yet achieved existence – into English, I might easily have saved myself a great deal of labor by having recourse to invented terms; in no case have I done so. Thus in many instances I have been forced to replace yet undiscovered concepts by their closest twenty-century equivalents. Such words as peltast, androgyn, and exultant are substitutions of this kind, and are intended to be suggestive rather than definitive.
He's right; the effect is very suggestive, and his decision not to go down the road of neologism is a linguistic triumph leading to a lavish feast of prose texture. But then he is writing about a far future Earth. If he had been writing about another world, neologisms would have been more appropriate.
The Ooranye Project has found it necessary to invent new words for some Uranian concepts. Here for example are two political neologisms to be found on the giant planet:
"Lremd" has connotations of luck and skill; it may be defined as the gift of being in the right place at the right time, of being able to weave one's way through a crowd of events without metaphorically bumping or jostling against other people. You could call it inbuilt personal radar. The Noads – city rulers – must possess this quality. It enables them to indulge every so often in adventures just as if they were private persons, and to keep in close touch with ordinary life. It follows marriages close to reality Rousseau's ambiguous idea of the "general will" in Du Contrat Social , an idea which on our world is impractical for any gathering larger than a group of friends. Thanks to lremd, government on Ooranye can be un-bureaucratic, not only free but free-and-easy, in a way that would be impossible on Earth!
"Arelk" is as bad as "lremd" is good. Arelk could be defined as a "political hardening of the treaties", whereby a polity degenerates into bureaucratic rigidity and temporary tyranny. Arelk is one of the phenomena most dreaded by the lremd-loving peoples of Ooranye.