(chemistry) A rule in chemistry that states that the sum of the hydrogen valence and the maximum oxygen valence is equal to eight.

(rail transport) synonym of ruling gradient

A narrow board with a plumb line fastened to the top, used to determine a perpendicular.

plural of plumb rule

plural of ruling grade

The principle that one should treat people the way they want to be treated, as opposed to the way you want them to treat you.

plural of work to rule

plural of sliding-rule

Dated form of slide rule.

An ecogeographical rule stating that latitudinal ranges of plants and animals are generally smaller at lower latitudes than at higher latitudes.