Several parts combine into one character.

感 is a phonetic-semantic compound: 咸 (xián, "all / completely") providing the sound, atop 心 (heart). The composite reads as "the heart in contact with everything" — the moment when external stimulus reaches inward and becomes registered, recorded, felt. 感 captures the moment of impression itself, before it crystallizes into a named emotion.

Korean reading "gam." Generates a remarkably wide vocabulary: 感情 (gamjeong, emotion), 感動 (gamdong, "being moved" — the gold standard for an inspiring artistic experience), 感覺 (gamgak, sensation / sense), 共感 (gonggam, empathy — increasingly central to Korean public discourse), 感謝 (gamsa, gratitude), 靈感 (yeonggam, inspiration). Korean 감 also appears as a colloquial loan: "감 잡았다" ("I got the 感") = "I get the gist."

Mandarin gǎn, 3rd tone. 感觉 (gǎnjué, feeling / sense), 感动 (gǎndòng, to be moved), 感谢 (gǎnxiè, to thank), 感觉到 (gǎnjuédào, "to feel / sense"), and the curious 感冒 (gǎnmào, "common cold") — literally "feeling exposed [to wind/cold]," reflecting traditional Chinese medicine's explanation of illness as the body being touched by external chill.

Japanese on-reading カン (kan) — 感情 (kanjō, emotion), 感動 (kandō, being moved / deeply impressed), 感謝 (kansha, gratitude), 直感 (chokkan, intuition). The verb 感じる (kanjiru, "to feel / sense") is built directly from this on-reading and is one of the most common Japanese verbs of inner experience: 寒さを感じる (samusa o kanjiru, "to feel the cold"). 感 has essentially no kun-reading — it lives entirely through Sino-Japanese compounds and the borrowed verb kanjiru.

Memory aid: heart (心) reached by all (咸) — sensation as the moment external touches internal.