adverb, takes genitive case の

  1. much more, still more, all the more, more than ever.

noun, takes genitive case の

  1. single layer (or story, etc.).

adverb

Archaism.
  1. rather, sooner, preferably.

Variations

Pronunciation Kanji Kana Is Common
一層 いっそう

Contained Kanji Breakdown

one, one radical (no.1)
イチ いっ ひと- (1st, N5)
stratum, social class, layer
ソウ (6th, N2)
corpse, remains, flag radical (no. 44)
シ かたしろ (Kentei 1)
formerly, once, before
ソ ソウ かつ (11th)
to divide
rice field, rice paddy
た デン たん (1st, N4)
day, sun, Japan
ひ ニチ にっ (1st, N5)