What is the difference between “jetzt” and “nun”?

[charred surge]

A sentence example would be helpful.

[pine forum]

in general synonyms, but "nun" can also be used differently, as in "nun ja" for example.

[ionic valve]

This is just an addition to the previous answer. Jetzt is a lot more common, especially in spoken German. You may find also that people use these words more or less often depending on where they come from.

[young scroll]

You see how interesting it is. I learned "jetzt" meant now, while "nun" meant "in the actual conditions". Thanks for your question, @charred surge.

One of the meanings of nun is according to DWDS exact the same as "jetzt". There are the one Atreides said and one rarer one you wont find very often ||it can mean als||.
Source for reference: https://www.dwds.de/wb/nun#1.

[cunning thorn]

1. Someone's car engine broke down Shit, nun kann ich nicht schwimmen gehen - Shit, now I can't go swimming (in this condition)
   2)Jetzt kann ich nicht schwimmen gehen - Now I can't go swimming (because i am busy (now/currently))

would these examples be correct?

[charred surge]

yes

[steel dust]

No, you can’t say “shit” in German

[cunning thorn]

anyways, a native speaker just confirmed these were normal sentences (on another server) and *shit * can be used in such a way. But it is less common than Sheiße. Hence it is not a mistake

[sharp lantern]

Yes these sentences are correct but I would just use jetzt in both ones as a native speaker because nun isn’t that common.
Using the english word shit while talking german is pretty common and just as realistic in this context as scheiße depends on the speaker