I've always hesitated over this. What is the difference in usage between encore and toujours when translating the word still, in the sense of “I still hate olives.”?
"Still" can indeed be translated by either encore or toujours but, depending on the context, both forms can have alternative meanings.
Instead of "still", encore might mean "again" while toujours might mean "always", e.g.:
- Je suis encore là = I'm still here or I'm here again
Je suis toujours là = I'm still here or I'm always here
J'ai encore faim = I'm still hungry or I'm hungry again
- J'ai toujours faim = I'm still hungry or I'm always hungry
There are cases where encore cannot be replaced by toujours. In such case, it can't be translated either by "still", e.g.:
- J'ai encore crevé = I had a flat tire again
Don't take that as a strict rule but to translate "still", you might prefer to use encore if the situation is more likely to change and use toujours if there is more continuity to expect.
Back to your example, if it is unlikely for your taste for olives to change, you would translate "I still hate olives." by:
- Je déteste toujours les olives.
but if there is some hope, that might be
- Je déteste encore les olives.
Instead of "still", encore might mean "again" while toujours might mean "always"
I agree for the essential but I would like to add yet other meanings.
encore might also mean something like "more"; e.g. encore mieux -> "even better", encore plus -> even further
(note that I didn't say that encore means "even" though: in those expressions its fundamental sense is closer to "more")
toujours might also sometimes stand for "already", like in c'est toujours ça de pris (which is equivalent to c'est déjà ça de pris); I'm not pretty sure of how it might be said in English, but Google gives me "it's still better than nothing", respectively "it's already better than nothing"