Yes and no
The three ways to answer a yes/no question, which you do in almost every exchange. It's a closed set, so the block stays at three.
un
polite haiyeah, uh-huh
うん はい
The casual yes, and also the 'uh-huh' you keep saying while someone talks to show you're following.
un, iku yo.
Yeah, I'm going.
うん、行くよ。
hai, ikimasu.
Yes, I'm going.
はい、行きます。
As a backchannel it shows you're listening, not that you agree; with superiors use hai (ee is the softer conversational polite yes). Trap: un confirms the statement, so to 'ikanai no?' (you're not going?) 'un' means 'right, I'm not going'.
uun
polite iieno, nope
ううん いいえ
The casual no to a yes/no question: two beats with a dip in pitch, while a short un means yes.
uun, ikanai yo.
Nope, I'm not going.
ううん、行かないよ。
iie, ikimasen.
No, I'm not going.
いいえ、行きません。
A long, flat uun (うーん, #298) means 'hmm'. The romaji is the same but it sounds different. To 'ikanai no?', 'uun, iku yo' means 'no, I AM going'.
iya
polite iieno, nah / well, no
いや いいえ
A firmer no than uun: it denies, corrects ('iya, chigau'), or opens a turn with 'well, actually'.
iya, chigau yo. ashita da yo.
No, no, it's tomorrow.
いや、違うよ。明日だよ。
iie, chigaimasu. ashita desu yo.
No, that's not right. It's tomorrow.
いいえ、違います。明日ですよ。
This is not the adjective iya 'unpleasant' (Versatile adjectives). In polite speech you mostly hear a short ie ('ie, daijoubu desu') or iya itself; full iie mostly answers a direct yes/no question.