1.
wavelength
The distance between successive crests of a wave, used in physics to describe light, sound, and other wave phenomena.
赤い光は波長が長い。
Red light has a long wavelength.
紫外線は短い波長の光である。
Ultraviolet light is light with a short wavelength.
電磁波の波長は種類によって大きく異なる。
The wavelength of electromagnetic waves varies greatly depending on the type.
2.
wavelength; compatibility; being on the same page
Used figuratively to describe how well two people's personalities, thinking styles, or communication mesh together.
彼女とは波長が合う。
I'm on the same wavelength as her.
初めて会ったのに、波長がぴったり合った。
Even though we met for the first time, we were perfectly in sync.
あの人とはどうも波長が合わなくて、話がかみ合わない。
I just can't seem to get on the same wavelength as that person — our conversations never quite click.
Has both a scientific and a figurative meaning. The figurative sense — describing interpersonal compatibility — is extremely common in everyday Japanese and often more frequently encountered than the physics sense.
COMMON COLLOCATIONS:
- 波長が合う: to be on the same wavelength; to click with someone
- 波長が合わない: to not be on the same wavelength; to not click
- 波長が長い/短い: to have a long/short wavelength (physics)
- 波長がぴったり合う: to be perfectly in sync
USAGE:
The figurative expression 波長が合う describes a natural, effortless compatibility between people — the feeling that conversation and interaction flow smoothly without conscious effort. It is a very natural and idiomatic expression, not stiff or technical sounding.
SIMILAR WORDS:
- 気が合う: to get along well — more general and common; focuses on temperament. 波長が合う implies a deeper, more instinctive connection in thinking style.
- 相性がいい: good compatibility — often used for romantic relationships or fortune-telling contexts. More evaluative than 波長が合う.