20 PREPOSITIONAL PHRASES IN ENGLISH WITH IN. A prepositional phrase is a group of words that begins with a preposition and ends with a noun, pronoun, or noun phrase. They are easy to learn because most of the time the meaning of the whole expression is clear from its parts. In this video, I suggest 20 prepositional phrases starting with "ON". They are common in everyday speech of all English speakers. For example, "on behalf of", "on purpose", "on one's own", "on average", "on holiday", "on business", "on my mind" , "on the point of", "on principle", "on the move", "on occasion", "on account of", "on reflection", etc. I hope the video will be of interest to you. Good luck!