由・よし

• 読み: よし
• ローマ字: yoshi
• 形: Verb plain form + 由 / ～とのよし / ～た由
• 漢字の分解: 由 (よし): reason, cause; by extension, reported information

意味

A dependent noun meaning 'it is reported that' or 'I have learned that,' used to mark the content of information the writer has received from another source. It conveys hearsay in formal written communication.

よし (written 由 in kanji) is a formal hearsay marker used predominantly in written Japanese, especially in business letters, official correspondence, and formal announcements. It attaches to a preceding clause (often in plain form or polite form) and signals that the writer is relaying information received from someone else. Common patterns include ～とのよし (I understand that), ～た由 (I have heard that), and ～の由 (it is reported that). Unlike そうだ (hearsay) or ということだ, which are appropriate across registers, 由 is reserved for formal written contexts and lends a distinguished, epistolary quality. It is rarely used in spoken Japanese.

例文

1. 先方から契約の見直しを希望している由、ご連絡がありました。
2. 部長がご出張中の由、改めてお伺いいたします。
3. 新工場の建設が順調に進んでいる由、安堵いたしました。

使い方ガイド

場面: written, business, correspondence

トーン: reportorial

正しい言い方

• ご退院なさった由、心よりお喜び申し上げます。
• 新任の部長がご着任された由、ご挨拶に伺いたく存じます。
• プロジェクトが無事完了した由、お疲れ様でございました。

避ける言い方

• 田中さんが来た由。(Using 由 in casual spoken context — it is restricted to formal written Japanese) → 田中さんが来たそうです。
• 明日は雨の由です。(Using 由 for a weather forecast — it is for relaying information received from a person, not impersonal sources) → 明日は雨だそうです。

起源と歴史

由 (よし) originally meant 'reason,' 'cause,' or 'means' in classical Japanese. Through its use in reporting the reasons and circumstances behind events, it came to function as a formal hearsay noun, especially in epistolary Japanese from the medieval period onward.

文化的背景

世代: All ages

社会的背景: Universal