有効

• Reading: ゆうこう
• Romaji: yuukou
• Kanji breakdown: 有 (yuu) — have, exist; 効 (kou) — effect, merit
• Pronunciation: /jɯː.koː/

Meaning

Valid; effective. Describes something that works well or is officially recognised.

A na-adjective with two main uses: (1) effective/useful — 有効な方法 (an effective method), 有効に活用する (to use effectively); (2) valid/in force — 有効期限 (expiry date), パスポートが有効 (the passport is valid). The opposite is 無効 (invalid/ineffective).

Examples

1. この薬は頭痛に有効だと言われている。 This medicine is said to be effective for headaches.
2. クーポンの有効期限は来月までだ。 The coupon's expiration date is the end of next month.
3. 時間を有効に使うことが大切だ。 It's important to use your time effectively.

Usage Guide

Context: medicine, business, legal

Tone: neutral

Origin & History

Compound of 有 (yuu, to have/exist) and 効 (kou, effect/merit). Together, 'having effect' — something that produces results or holds official standing.

Cultural Context

Era: Classical

Generation: All ages

Social background: Universal