요: Polite particle

Is 요 a particle or an ending?

Most learners meet 요 at the end of verbs, so it's natural to think of it as an ending. Korean dictionaries list it as a particle, though, because it attaches to almost anything: a noun (커피요, keopiyo), an adverb (빨리요, ppalliyo), or a sentence that's already finished in casual speech. 좋네요 jonneyo is the casual 좋네 jonne plus 요, and 먹을까요? meogeulkkayo is 먹을까? meogeulkka plus 요. Take it off and the sentence becomes casual:

• 날씨 좋네요. nalssi jonneyo "Nice weather, isn't it?" Polite.
• 날씨 좋네. nalssi jonne Same thing, to a friend.

The everyday 아요/어요 ayo/eoyo in 가요 gayo and 먹어요 meogeoyo is a little different: the dictionary lists it as one whole ending rather than as this particle. That's covered in the post on Korean verb conjugation.

After a consonant: 라면요 or 라면이요

After a noun that ends in a consonant, you can add 요 straight on, as in 라면요 ramyeonyo, "ramen, please", or use 이요: 라면이요 ramyeoniyo. The national dictionary accepts both, and 라면이요 is what you'll hear most in speech.

아니요, not 아니오

The polite "no" is 아니 ani plus 요, so it's spelled 아니요 aniyo. 아니오 is an old-fashioned sentence ending that you'll only see on some forms and quizzes.