Several parts combine into one character.

漢 began as the name of a single river — the Han River (漢水, Hànshuǐ) flowing through central China, which gave its name to a city, then to the dynasty (Han Dynasty, 206 BCE – 220 CE) founded with that city as capital. Over four centuries of imperial rule, the dynasty's name became the name of the dominant ethnicity (Han Chinese), then of the language they spoke (Han speech = Chinese), then of the writing system they used (Han characters = Chinese characters). One river name expanded outward to label the cultural identity of an entire civilization. The 氵 (water) radical preserves its hydrographic origin. Mainland simplified to 汉.

Korean reading "han." 漢字 (hanja, Chinese characters as used in Korean), 漢文 (hanmun, classical Chinese text), 漢族 (hanjok, Han ethnic Chinese), 漢方 (hanbang, Korean traditional medicine — note the Sino-Korean paradox: Korean traditional medicine carries the "Han" Chinese label even while Koreans assert its distinct lineage). And 漢江 (Hangang, the Han River that flows through Seoul) — though the Chinese 漢水 and Korean 한강 are not directly etymologically related, the same character is used because the Korean Hangang means "the great river that flows through the capital." The character creates an apparent connection between two unrelated rivers across two countries.

Mandarin hàn, 4th tone (simplified 汉). 汉字 (hànzì, Chinese characters), 汉语 (hànyǔ, Chinese language), 汉族 (Hànzú, Han ethnicity — about 92% of mainland Chinese citizens), 汉朝 (Hàncháo, Han Dynasty). Modern Mandarin also uses 汉 in the slang sense of "manly fellow / tough guy": 男子汉 (nánzǐhàn, "real man"), 好汉 (hǎohàn, "fine fellow / hero" — famously used in Outlaws of the Marsh / Water Margin), 醉汉 (zuìhàn, drunkard). The "manly" sense is uniquely Mandarin colloquial.

Japanese on-reading カン (kan) — 漢字 (kanji, Chinese characters as used in Japanese — the global standard term), 漢方 (kanpō, Chinese-style herbal medicine — heavily integrated into Japanese pharmacy and remedy traditions), 漢詩 (kanshi, Classical Chinese poetry composed by Japanese authors), 漢民族 (kanminzoku, Han ethnicity). The Japanese term 漢字 — kanji — has become the worldwide loanword English uses for Chinese characters in any East Asian context, even displacing the equally accurate term hanzi. Every character in the Lingua / Glyph Garden you are reading is a kanji.

Memory aid: water (氵) — this character begins as a river name, expands to a dynasty, an ethnicity, a language, and a writing system. One river became a civilization's label.