The term 'COMPARATIVE ENDING' refers to the suffixes used to form comparative adjectives and adverbs. The two most common comparative endings are 'IER' and 'IOR'. These suffixes are added to the end of a word to indicate that something is more or less than something else. For example, adding 'IER' to the word 'HAPPY' would create the comparative adjective 'HAPPIER', indicating that something is more HAPPY than something else. Similarly, adding 'IOR' to the word 'QUICK' would create the comparative adverb 'QUICKER', indicating that something is more QUICK than something else.