nother
Nother (adj) means a different one; another one (used informally, often in the phrase "a whole nother"). Example: “That's a whole nother problem we haven't even talked about yet.”
How to use nother
Learner’s notesIn plain EnglishAn informal way of saying "another," almost always heard in the set phrase "a whole nother."
Very informal — fine in casual speech, but avoid it in formal writing where "another" is correct.
Fill the gap
Can you complete this real example?
That's a whole _____ problem we haven't even talked about yet.
Etymology
A playful English reshuffling of "an other" into "a nother" — the same kind of sound-swap that turned "a napron" into "an apron."