返還【へんかん】
return, restoration
帰還【きかん】
return (home), repatriation, feedback (in an electronic circuit, biological system, etc.)
還元【かんげん】
restoration, return, reduction, resolution, deoxidization, deoxidation
奪還【だっかん】
recapture, retaking, recovery, taking back
還暦【かんれき】
kanreki, one's 60th birthday (or 61st in the traditional age reckoning system) when one has lived through a full sexagenary cycle