rule

n. & v.
—n.
1 a principle to which an action conforms or is required to conform.
2 a prevailing custom or standard; the normal state of things.
3 government or dominion (under British rule; the rule of law).
4 a graduated straight measure used in carpentry etc.; a ruler.
5 Printing a a thin strip of metal for separating headings, columns, etc. b a thin line or dash.
6 a code of discipline of a religious order.
7 Law an order made by a judge or court with reference to a particular case only.
8 (Rules) Austral. = Australian Rules.
—v.
1 tr. exercise decisive influence over; keep under control.
2 tr. & (foll. by over) intr. have sovereign control of (rules over a vast kingdom).
3 tr. (often foll. by that + clause) pronounce authoritatively (was ruled out of order).
4 tr. a make parallel lines across (paper). b make (a straight line) with a ruler etc.
5 intr. (of prices or goods etc. in regard to price or quality etc.) have a specified general level; be for the most part (the market ruled high).
6 tr. (in passive; foll. by by) consent to follow (advice etc.); be guided by.
Phrases and idioms:
as a rule usually; more often than not. by rule in a regulation manner; mechanically. rule of the road see ROAD(1). rule of three a method of finding a number in the same ratio to one given as exists between two others given. rule of thumb a rule for general guidance, based on experience or practice rather than theory. rule out exclude; pronounce irrelevant or ineligible. rule the roost (or roast) be in control. run the rule over examine cursorily for correctness or adequacy.
Derivatives:
ruleless adj.
Etymology: ME f. OF reule, reuler f. LL regulare f. L regula straight stick