ローム層[roomusou] stratum of loam
亜成層圏[aseisouken] substratosphere
一層[issou] much more
沖積層[chuusekisou] alluvium
下層[kasou] lower strata (classes)

下層階級[kasoukaikyuu] proletariat
下層社会[kasoushakai] the underworld
下層土[kasoudo] subsoil
化石層[kasekisou] fossil bed
階層[kaisou] class

いい年をして[iitoshiwoshite] (in spite of) being old enough to know better
亥年[idoshi] year of the boar
一箇年[ikkanen] one year
一周年[isshuunen] one full year
一年以内に[ichineninaini] within a year

一年間[ichinenkan] (period of) one year
一年生[ichinensei] annual (plant)
一年草[ichinensou] annual (plant)
一年ぢゅう[ichinenjuu] all year round
一両年[ichiryounen] (a) year or two

加齢[karei] adding to one's years
学齢[gakurei] school age
月齢[getsurei] age of the moon
高齢[kourei] advanced (old) age
弱齢[jakurei] youth

寿齢[jurei] long life
樹齢[jurei] age of a tree
就学年齢[shuugakunenrei] school age
適齢期[tekireiki] marriageable age
年齢差[nenreisa] age difference