A polysyllabic word is a word you can clap into three or more beats.

A polysyllabic word多音節的字， is是 a word you can clap into你可以拍成 three or more beats三拍或三拍以上的字。

Cat is one beat. Happy is two. Computer is three, so it is polysyllabic.

Cat貓 is是 one beat一拍。Happy開心 is是 two beats兩拍。Computer電腦 is是 three beats三拍， so所以 it is polysyllabic它就是多音節的。

This is a school and dictionary word, not a word you use when you buy fruit. You meet it in spelling class, in poetry, and when a teacher is talking about “long words.” Though actually, some language people use it more loosely: for them, any word with more than one beat counts, so happy would be in too.

This這 is a school and dictionary word是課堂和字典裡會用的詞， not a word you use when you buy fruit不是你去買水果時會用的字。in spelling class在拼字課、 in poetry詩裡， or when a teacher is talking about 'long words'或老師在講「長字」的時候， you你 meet it會遇到它。Though actually不過其實 some language people有些語言學家 use it more loosely用得比較鬆： any word with more than one beat只要一個字超過一拍 counts就算， so所以 happy happy would be in too也算在內。

Learner books, and this sense, usually keep it for three or more.

Learner books學習者用的書， and this sense還有這個意思， usually keep it for three or more通常把它留給三拍或以上。

People also stretch it as a joke: they call a show-off, heavy word “polysyllabic” even when they only mean “it sounds fancy,” not that they have counted the beats.

People人們 also stretch it as a joke也會開玩笑地把它用得更誇張： they他們 call a show-off, heavy word會把一個愛炫耀、很重的字 'polysyllabic'叫做「多音節的」， even when they only mean 'it sounds fancy,'就算他們只是想說「聽起來很花俏」， not that they have counted the beats並不是真的數過拍子。