Literary expression emphasizing extreme brevity, like dew that vanishes quickly. Often used in set phrases such as 露の間も忘れない (not forget even for a moment).
I have never forgotten him even for a moment.
That beauty vanished like a fleeting dream.
Standard kanji spelling; literally 'dew's interval', evoking brevity.
Kana spelling is common in everyday writing, especially when the poetic nuance of 露 is not needed.
Compound of 露 (つゆ, 'dew') + の (possessive particle) + 間 (ま, 'interval, time'). The image is of a time as brief as the morning dew, which evaporates quickly.