衰頽[suitai] decline
頽れる[sutareru] to go out of use
頽廃[taihai] degeneration
頽勢[taisei] one's declining fortunes
廃頽[haitai] decay

頽唐[taitou] decadence
頽齢[tairei] declining years
胡頽子[gumi] oleaster (any plant of genus Elaeagnus)
人倫頽廃[jinrintaihai] decline (decay, corruption) of ethical standards
風紀頽廃[fuukitaihai] decay (decline, corruption) of public morals

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