Several parts combine into one character.

岩 is a compound ideograph stacking 山 (mountain) over 石 (stone) — the stone that makes up a mountain, that is, a boulder or crag. With 山 and 石 plainly visible, its meaning is transparent. An older form 嵒 (three stones atop a mountain) also existed, but the simpler 岩 became standard.

Korean hanja-sound "am": 岩石 (amseok, rock), 火成岩 (hwaseongam, igneous rock), 堆積岩 (toejeogam, sedimentary rock), 變成岩 (byeonseongam, metamorphic rock), 鎔岩 (yongam, lava). The whole geological classification of rock uses this character.

Mandarin: yán, 2nd tone. 岩石 (yánshí, rock), 岩浆 (yánjiāng, magma), 熔岩 (róngyán, lava).

Japanese: on-reading ガン (gan), kun いわ (iwa). 岩 (iwa, boulder), 岩石 (ganseki, rock), 溶岩 (yōgan, lava), 岩場 (iwaba, rocky ground). It is common in surnames — 岩田 (Iwata), 岩崎 (Iwasaki, founders of Mitsubishi).

Memory aid: stone (石) beneath a mountain (山) — the great stone that makes up a mountain, a boulder.