Relax

くつろがせる

kutsurogaseru

((transitive) to make something loose)

和らげる

yawarageru

((transitive) to make something less severe or tense)

緊張を解く

kinchō wo toku

((transitive) to make something less severe or tense)

落ち着かせる

ochitsukaseru

((transitive) to make something less severe or tense)