On

• on a higher floor • on a lower floor • on a par • on a regular basis • on account of • on air • on all fours • on an individual basis • on an irregular basis • on and off • on and on • on approval • on average • on base • on board • on call • on camera • on dit • on duty • on earth • on edge • on end • on faith • on fire • on guard • on hand • on high • on ice • on it • on land • on leave • on occasion • on one hand • on one's guard • on paper • on purpose • on record • on request • on tap • on tenterhooks • on that • on that point • on the alert • on the average • on the ball • on the beam • on the brink • on the button • on the coattails • on the contrary • on the dot • on the double • on the face of it • on the far side • on the fence • on the fly • on the fritz • on the go • on the hook • on the house • on the job • on the level • on the lookout • on the lookout for • on the loose • on the move • on the nose • on the offensive • on the one hand • on the other hand • on the q.t. • on the qt • on the qui vive • on the rag • on the road • on the rocks • on the run • on the shelf • on the side • on the sly • on the spot • on the spur of the moment • on the table • on the verge • on the wagon • on the wane • on the way • on the whole • on the wing • on time • on to • on tour • on trial • on trust • on your guard