Several parts combine into one character.

In oracle bone script, 愛 is one of the most architecturally beautiful characters in the entire CJK system. From top to bottom: 爫 (a hand reaching down), 心 (a heart in the middle), and 夂 (a foot walking slowly). The composite reads vertically as a single image — a hand cradling a heart, carrying it forward with slow, deliberate steps. The ancient Chinese definition of love was not a feeling but an action: tenderly holding what is most fragile and walking carefully so as not to drop it. Mainland simplified to 爱 — and notoriously, the simplification removed the 心 (heart) component, prompting the famous CJK joke that "modern Chinese love has no heart."

Korean reading "ae." Saturates the vocabulary of affection: 愛人 (aein, lover / sweetheart), 愛情 (aejeong, affection), 愛國 (aeguk, patriotism), 戀愛 (yeonae, romance / dating), 寵愛 (chongae, royal favor), 愛憎 (aejeung, "love and hate" — the dual nature of intense feelings).

Mandarin ài, 4th tone (simplified 爱). 我爱你 (wǒ ài nǐ, "I love you") is the universal romantic phrase. 爱情 (àiqíng, romantic love), 爱国 (àiguó, patriotic), 喜爱 (xǐ'ài, to be fond of), 亲爱的 (qīn'ài de, dear / beloved). The character is also used colloquially as "to be willing / to like to" — 我爱吃辣 (wǒ ài chī là, "I love eating spicy food").

Japanese on-reading アイ (ai) — 愛情 (aijō, affection), 愛犬 (aiken, beloved dog), 恋愛 (ren'ai, romance), 愛人 (aijin — note this is a false friend with Korean: in Japanese it specifically means "lover / mistress" with affair connotations, NOT spouse). The kun-readings are essentially extinct in modern Japanese; love is expressed with the borrowed-into-grammar 愛してる (aishiteru, "I love you"). Note that 愛してる carries unusual gravity in Japanese — it is reserved for serious romantic declarations and rarely used casually.

Memory aid: a hand cradling a heart, walking carefully — love as the slow, deliberate carrying of what is precious.