Several parts combine into one character.

對 (traditional) comes from holding something like a lamp-stand or instrument-rack upright and facing with the hand (寸), giving "to face, to answer, a pair, to deal with." It began from setting things up to face and pair.

The form splits three ways: traditional (ko/en/es) is 對, Japanese shinjitai (ja) is 対, Chinese simplified (zh) is 对 — the left part differs by mode (對 14 strokes vs 対 7 vs 对 5).

Korean hanja-sound "dae": 對話 (daehwa, conversation), 反對 (bandae, opposition), 對象 (daesang, object / target), 絶對 (jeoldae, absolute), 對應 (daeeung, response), 相對 (sangdae, relative), 對策 (daechaek, countermeasure). Korea uses the traditional 對.

Mandarin: duì, 4th tone. 对 (duì, correct / right), 对面 (duìmiàn, opposite side), 对话 (duìhuà, dialogue), 反对 (fǎnduì, to oppose), 对不起 (duìbuqǐ, sorry). In modern Chinese 对 (duì) is used daily as the affirmative "right / correct" — 对！ (Right!).

Japanese: on-readings タイ (tai) and ツイ (tsui), kun あいて (aite). 対話 (taiwa, dialogue), 反対 (hantai, opposition), 対象 (taishō, object / target), 一対 (ittsui, a pair — a ツイ reading), 対面 (taimen, meeting face to face). A pair is counted 一対 (ittsui).

Memory aid: holding something upright and facing with the hand (寸) — a character that splits into traditional 對 / shinjitai 対 / simplified 对.