noun, adjectival noun or quasi-adjective, takes genitive case の

Poetical term.
  1. eternity, perpetuity, permanence.

Variations

Pronunciation Kanji Kana Is Common
永久 とわ
永遠
永遠 とわ
とわ

Contained Kanji Breakdown

eternity, long, lengthy
エイ なが.い え (5th, N2)
dot, tick or dot radical (no. 3)
チュ (Kentei 1)
water
みず スイ み (1st, N5)
long time, old story
ひさ.しい ひさ キュウ (5th, N2)
wrapping enclosure(勹) variant