Но and или: but and or

но: but, against expectation

Но is the real but. The second half goes against what the first led you to expect:

• Я хочу́ пойти́, но не могу́. - I want to go, but I can't.
• Уже́ по́здно, но он рабо́тает. - It's late, but he's still working.
• Э́то тру́дно, но интере́сно. - It's difficult but interesting.

The test that settles almost every case: is there a despite in the meaning? Despite wanting to, I can't. If yes, но. If you are merely comparing two things, а.

In speech а can carry a note of surprise, Уже́ по́здно, а он рабо́тает. (it's late, and he's still working!), but но is never wrong when there is a despite.

One fixed pair breaks the not-X-but-Y rule, because nothing is being cancelled, only extended:

• Я не то́лько говорю́, но и пишу́. - I not only speak but also write.

Two relatives of но are worth recognising:

или: or

Или (ili) is or, and behaves like its English equivalent. Doubled, it gives either... or:

• Чай и́ли ко́фе? - Tea or coffee?
• И́ли ты, и́ли я. - Either you or me.

The negative partner, neither... nor, is ни... ни, and it brings a не before the verb with it:

• Ни я, ни он не зна́ем. - Neither he nor I know.

Russian negation covers ни and the double negative it belongs to.