A very large stone, usually roundish or worn smooth, big enough that you could not pick it up — often as tall as a person, or bigger. Rain, rivers, and time knock the sharp corners off, so a boulder looks different from a freshly broken chunk of cliff.

A very large stone一顆很大的石頭，usually roundish or worn smooth通常圓圓的或被磨得很光滑，big enough that you could not pick it up大到你根本搬不動——often as tall as a person, or bigger常常跟一個人一樣高，甚至更大。Rain, rivers, and time knock the sharp corners off雨水、河流和時間會把尖銳的稜角磨掉，so a boulder looks different from a freshly broken chunk of cliff所以boulder看起來跟剛從懸崖崩落的碎塊不一樣。

You find them in rivers, on beaches, on mountainsides. People also climb on them; that close-to-the-ground climbing took the name bouldering from this stone.

You find them in rivers, on beaches, on mountainsides你會在河裡、海灘上、山坡上找到它們。People also climb on them人們也會爬這種石頭；that close-to-the-ground climbing took the name bouldering from this stone這種貼近地面的攀爬運動，名字bouldering（抱石）就是從這種石頭來的。

A city in the United States is called Boulder after rocks like these. Everyday English uses boulder loosely for ‘huge rock’. Scientists draw stricter size lines (a boulder is larger than a cobble), but a learner only needs ‘a big, heavy, often rounded rock’.

A city in the United States is called Boulder after rocks like these美國有一座城市叫Boulder，就是因為這種石頭而得名。Everyday English uses boulder loosely for 'huge rock'日常英文用boulder時比較鬆散，泛指「巨大的石頭」。Scientists draw stricter size lines科學家會畫出更嚴格的大小界線（a boulder is larger than a cobbleboulder比cobble大），but a learner only needs 'a big, heavy, often rounded rock'不過學習者只要記得「又大又重、通常圓圓的石頭」就夠了。