由(よし)reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...

連(つ)れ去(さ)られた子供(こども)の行方(ゆくえ)は知(し)る由(よし)もない。

There is no way to know the whereabouts of the abducted child. {reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...}

由(よし)ありげな様子(ようす)の彼女(かのじょ)は、なんだか怪(あや)しいです。

She, seeming to have some reason or cause, is somehow suspicious. {reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...}

部下(ぶか)：「田中(たなか)さん！社長(しゃちょう)にこの由(よし)をお伝(つた)えしてください。」

Subordinate: "Mr. Tanaka! Please convey this reason to the president." {reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...}

訪問(ほうもん)客(きゃく)：「体調(たいちょう)を心配(しんぱい)していましたが、お元気(げんき)の由(よし)、何(なに)よりです。」

Visitor: "I was concerned about your health, but it is wonderful to hear that you're well." {reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...}

彼女(かのじょ)には散々(さんざん)嫌(いや)な思(おも)いをさせられたのだから、会(あ)う由(よし)なんてありません。

I have no reason to meet her because she has made me feel terrible. {reason, significance, cause, piece of information that one has heard, I hear that ..., it is said that ...}