Denshi Jisho — Online Japanese dictionary

知る しる to know; to understand; to be acquainted with; to feel
Common word, Godan verb with ru ending, Transitive verb 
知る辺 しるべ acquaintance; friend
Noun 
知る限り しるかぎり as far as I know
Expression 
知る人ぞ知る しるひとぞしる Those in the know, know it very well (though it isn't known to many people)
Expression, Idiomatic expression 
知る由もない しるよしもない to have no way of knowing; to be completely ignorant of
Expression 

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