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.

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.

The ecogeographic principle that, within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions.

(obsolete) Algebra.

(gematria, very rare in print) The rule according to which one digit may be added to or subtracted from the gematric value of a word.

(UK) Solitary confinement imposed to protect a vulnerable prisoner from other inmates.

(finance) Of a deal: concluded by the secretary of the stock exchange when the actual dealer has failed to do so.

(UK, politics) A constitutional convention (which acquired legal force in 2010) dictating that most international treaties had to be laid before Parliament 21 days before ratification.

Synonym of island rule