A megalith is a very large stone that ancient people stood up or set in place — not a rock that happened to be there, but one that human beings chose, moved, and arranged. Stonehenge in England is the famous example; you also find them across Europe, in Korea, and elsewhere. Some stand alone, some form circles or lines, some are propped together to make a stone room over a grave. We do not know for certain why they were built, and honest writers say so: religious ceremony, burial, marking the seasons or the sun's position, showing who held power — all likely, none proven. The word is mostly written rather than spoken; it belongs to history books, museum signs, and archaeology programmes rather than daily talk. People sometimes stretch it to mean any huge organisation or building that feels immovable and old — 'the banking megalith' — but that use is closer to 'monolith', and 'monolith' is the word most speakers reach for there.

巨石（史前人類豎立的大石，如英國巨石陣的石柱）