介入【かいにゅう】
intervention
紹介【しょうかい】
introduction, presentation, referral
仲介【ちゅうかい】
agency, intermediation
介在【かいざい】
existing (between), interposition, intervention, involvement
厄介【やっかい】
trouble, burden, nuisance, bother, worry, care, dependence, support, kindness, obligation, staying (with a person)
媒介【ばいかい】
mediation, agency, serving as a medium, acting as an intermediary, acting as a go-between, carrying (germs, diseases, etc.), transmission, mediation (in Hegelianism)
自己紹介【じこしょうかい】
self-introduction
一介【いっかい】
mere, only a ...
魚介【ぎょかい】
marine products, seafood, fish and shellfish