A ruler is a tool used to measure length, typically in inches or centimeters. In English, you can say "Where is the ruler?" or "Can you pass me the ruler?"

The word "ruler" comes from the Latin word "regula," which means "straight stick." It has been used in English since the late 13th century.

Here are some example sentences with the word "ruler" in English:

"I need a ruler to measure this piece of wood." (我需要一把尺子来测量这块木头。)

"The ruler has markings on it so you can measure in inches or centimeters." (尺子上有刻度，所以你可以用英寸或厘米测量。)

"I accidentally dropped the ruler and it broke in half." (我不小心把尺子掉了，它断成两半了。)