on

short for \ shortened from \ shortened version of the prepositional phrase ‘on {TV}’ or ‘on {TV network-X}’. Preposistion used as a present-tense_particple-type adjective in sentences that answer or pose (dependent on whether the sentence is declarative or interrogative) the question as to ‘*When* {<a designated program> is on <television>}’. This is an example of a shortened version of something which is repeatedly said over-and-over in English; another example is the ommition of 'that' or 'which' in the sense of “Why is it, that you always seem to be attracted the to food *I* like?”, which actually means “Why is it, that you always seem to be attracted the to food that\which *I* like?” Not exactly the same are these two, though similar enough to be compared, I feel.