Adage
An adage was a type of saying made as a concise observation that expressed a general truth, piece of advice, or rule of conduct. 

Gannet had a rule she shared with Travis Mayweather, "If I'm in bed with someone, they have to be in bed with me." ()

In preparing Wesley Crusher to become a leader, Deanna Troi explained that "Leadership grows from self-confidence", but the situation also reminded Jean-Luc Picard that "there is an old horse trainer's adage about putting too much weight on a young back. We don't want him to break under pressure." ()

Robin Lefler established a written copy of personal rules that she used as a personal guide through life, which she called, "Robin's Laws". ()

Adages 
"Be careful what you wish for"
 In 2285, after "Mr. Adventure" complained that he wanted more challenges, adventure and surprises in his life, Uhura said "You know what they say, 'Be careful what you wish for. You may get it." and locked him in a closet. ()

In 2373, upon Tom Paris saying to B'Elanna Torres that he wouldn't mind seeing her Klingon side again, Torres warned him to be careful what he'd wished for. ()

 In 2377, when 204 Klingons came aboard Voyager, Torres said that she should be careful what she wished for, after six years of feeling uncomfortable being the only Klingon aboard for. ()

"Finders, keepers."
 

"Look before you leap." 
 Specifically, "to look before I leap," was claimed to be an antiquated adage by Seven of Nine. ()

"Patience is sometimes a more effective weapon than the sword."
 

"The best defense is a good offense." 
 James T. Kirk spoke of a variation of this adage, "the best defense is a strong offense, and I intend to start offending right now," when he, Spock and Gem were held in Vian captivity. ()
 Described as a phrase by The Doctor, he used it to explain to Seven of Nine that "Throughout human history weapons of mass destruction were often designed in the hopes that they'd never be used," when facing the prospect of dealing with Species 8472. ()

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Linguistics