The mainsail is the biggest sail on a sailing ship — the one that does most of the work of catching the wind. It hangs from the mainmast, the tallest mast, usually near the middle of the ship. Sailors treat it as one word.

The mainsail主帆（mainsail） is the biggest sail on a sailing ship是帆船上最大的一面帆 — the one that does most of the work of catching the wind是做大部分抓風工作的那一面。It hangs from the mainmast它掛在mainmast, the tallest mast最高的那根桅杆, usually near the middle of the ship通常在船身中間附近。Sailors treat it as one word水手把它當成一個字看待。

Which sail counts as the mainsail depends a little on the kind of boat: on a simple sailing boat it is obvious; on a tall ship with many sails, it is still the large one on that mainmast. People sometimes say it loosely for whatever sail they are using most, but in careful sea language it names that particular sail.

Which sail counts as the mainsail哪一面帆算是mainsail depends a little on the kind of boat多少要看是哪種船：on a simple sailing boat在簡單的帆船上 it is obvious這很明顯; on a tall ship with many sails在有很多帆的大船上, it is still the large one on that mainmast它仍然是那根mainmast上最大的那一面。People sometimes say it loosely人們有時候會鬆散地用它 for whatever sail they are using most指自己用得最多的帆, but in careful sea language但在講究的航海用語裡 it names that particular sail它專指那一面特定的帆。

You will meet it in ship stories and sailing talk, not in ordinary city English.

You will meet it你會遇到它 in ship stories and sailing talk在船的故事和航海的談話裡, not in ordinary city English不是在一般都市英語裡。