If you are double-jointed, some of your joints can bend farther than most people’s — fingers that fold back toward the wrist, elbows or knees that look as if they bend a little the “wrong” way. It looks as if that body part had two joints working in different directions, which is how the word was built; there are not actually two joints.

If如果 you are double-jointed你是雙關節的人 some of your joints你有些關節 can bend farther than most people's可以彎得比大多數人還遠 fingers that fold back toward the wrist像是手指可以往手腕折回去 elbows or knees手肘或膝蓋 that look as if they bend a little the "wrong" way看起來像是往「錯」的方向彎一點點 It looks as if它看起來像 that body part那個部位 had two joints working in different directions有兩個朝不同方向動的關節 which is how the word was built這個詞就是這樣來的 there are not actually two joints但其實並沒有兩個關節

Some people do party tricks with it; for others it is just very flexible joints.

Some people有些人 do party tricks with it會用它表演小把戲 for others對其他人來說 it is just very flexible joints這只是關節特別軟

Informal, everyday. Doctors have more careful names (hypermobile joints), but this is the word students will hear.

Informal, everyday口語、日常的說法 Doctors have more careful names醫生有更嚴謹的說法 (hypermobile joints)（hypermobile joints，關節過動） but this is the word students will hear不過學生會聽到的就是這個詞

It can be handy, or it can mean the joint is a bit less stable — both happen.

It can be handy它可以很方便 or it can mean或者也可能代表 the joint is a bit less stable關節穩定度差一點 both happen兩種情況都有