What is the difference between a ruler and a rule?

What is the difference between a ruler and a rule?

As nouns the difference between ruler and rule is that ruler is a (usually rigid), flat, rectangular measuring or drawing device with graduations in units of measurement; a rule; a straightedge with markings; a measure while rule is a regulation, law, guideline.

What is a straightedge used for?

A straightedge or straight edge is a tool used for drawing straight lines, or checking their straightness. If it has equally spaced markings along its length, it is usually called a ruler.

Why is a ruler called a ruler?

Why is a ruler (measuring device) called a ruler? "Ruler" is just a 15th century variation of "rule," which comes, via French, from Latin "regula," which meant a measuring stick, a diminutive derived from "regere," to straighten, lead, or guide. The word "rule," comes from the same source, but is more metaphorical.