an object such as a ruler or a piece of wood, used for drawing or checking straight lines

Use a straight edge for cutting the fabric. 裁剪布料时要用直尺。

having an edge that is straight rather than curved or irregular

Use a straight-edge knife. 需要用直刃刀。

having a way of life that does not involve doing anything considered to be unhealthy or immoral

He's very straight edge now - no drinking, no smoking. 他现在生活很健康——不喝酒，不抽烟。