Other forms: rules, ruled, ruling
A rule is a statement of what you may and may not do. The rules of the game, school rules, against the rules, break a rule.
As a verb it means to govern — the family that ruled for two centuries — and also to give an official decision: the judge ruled that the evidence was inadmissible. There is a third, physical sense: to rule a line is to draw it with a ruler, which is where ruled paper comes from and which is the oldest meaning of all. Note as a rule, meaning usually, and rule out, meaning to eliminate a possibility, which is among the most useful phrasal verbs in careful writing.
1nounruleA statement of what is allowed and what is not.
“There is a rule about phones in the exam hall.”
synonyms: regulation, law
2verbgovernTo govern a country or a people.
“The dynasty ruled for four hundred years.”
3verbgiveTo give an official decision.
“The court ruled in her favour.”
4nounnormalThe normal state of things.
“Late trains are the rule rather than the exception here.”
Too few real examples of this word to estimate which sense is commonest.
rule is a statement of what is allowed.
Latin regula meant a straight stick — a ruler for drawing lines. From the physical straightedge came the idea of a standard to measure conduct against, and from that the modern rule. The same root gives regular, regime and rectangle: everything straight.
Proto-Indo-European
*h₃reǵ-
Proto-Indo-European
*h₃réǵeti — to straighten; right
Latin
regula — straight stick, bar, ruler, pattern
Old French
riule
Middle English
reule
English, today
rule
Built from
From Middle English reule, rewle, rule, borrowed from Old French riule, reule, from Latin regula (“straight stick, bar, ruler, pattern”), from regō (“to keep straight, direct, govern, rule”), ultimately from Proto-Indo-European h₃réǵeti (“to straighten; right”), from the root h₃reǵ-; see regent. a doublet of rail and regal#Noun and regula and rigol.
Etymology from Wiktionary, CC BY-SA