弓弦bowstring

• 弦绷得还不够紧。

  The bowstring still isn't taut enough.

乐器的弦string

• 弦声

  twang

发条spring

• 我的表弦断了。

  The spring in my watch has broken.

• 别忘了给闹钟上弦

  don't forget to wind the alarm clock

连结圆周上两点的直线【数】chord

直角三角形的斜边【数】hypotenuse