과/와
RuleNoun + gwa/wa: links nouns ("A and B") or means "together with." After a consonant use gwa; after a vowel use wa.
Curiosity
ppang-gwa uyu ("bread and milk") uses gwa, but sagwa-wa bae ("apple and pear") uses wa. Same "and" — why two shapes?
Intuition
Just like the other particles, the final sound of the preceding noun decides the shape: gwa after a consonant, wa after a vowel — smoothing the join in pronunciation.
Visualization
See which form attaches to a consonant-final noun (ppang) versus a vowel-final one (sagwa): ppang → ppang-gwa, sagwa → sagwa-wa.
Roleand / with
ends in a consonant빵bread
ends in a vowel사과apple
Essence
gwa/wa is somewhat formal; in speech hago or (i)rang are more common — hago never changes, while (i)rang alternates as irang/rang by batchim. It also means "with," as in chingu-wa gachi ("together with a friend").
Examples
빵과 우유를 샀어요.
I bought bread and milk.
사과와 배가 있어요.
There are apples and pears.
친구와 같이 영화를 봐요.
I watch a movie together with a friend.
Mini-quiz
"ppang__ uyu" (bread and milk) — which fits the blank?