波長

• Reading: はちょう
• Romaji: hachō
• Kanji breakdown: 波 (ha/nami) — wave; 長 (chō/naga-) — length, long
• Pronunciation: /ha.tɕoː/

Meaning

Wavelength; the distance between successive crests or troughs in a wave. Informally, also used to mean being on the same wavelength, i.e. mutual understanding or rapport.

A noun with both precise scientific usage and a common figurative sense. In physics, wavelength (λ) determines the energy and properties of electromagnetic radiation — visible light occupies 380–780 nm. In everyday speech, 波長が合う means two people think alike or get along well. This dual usage makes 波長 one of the more versatile scientific terms in Japanese.

Examples

1. 紫外線は可視光より波長が短く、皮膚細胞のDNAにダメージを与えることがある。 Ultraviolet light has a shorter wavelength than visible light and can damage the DNA in skin cells.
2. レーザー光は単一の波長の光を位相を揃えて放射するため、強い指向性を持つ。 Laser light emits a single wavelength of light with aligned phase, giving it strong directionality.
3. 彼女とは初対面から波長が合い、すぐに打ち解けることができた。 She and I were on the same wavelength from the moment we met, and we hit it off right away.

Usage Guide

Context: physics, optics, daily life, interpersonal relations

Tone: neutral

Origin & History

Compound of 波 (ha — wave) and 長 (chō — length). A Meiji-era coinage that directly translates the concept of the spatial period of a wave.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal