What is an analogy? The definition of analogy is an expression of similarity between two unlike things. Usually the comparison involves two or more comparison points. In real life, analogies are used to explain and teach. Their most common uses are to Explain something unknown in terms of something known. Explain something unfamiliar in terms of something familiar. Explain something unseen in terms of something seen. An analogy usually does more than describe the appearance of something; it explains how something works. Analogies usually oversimplify to give an frame of reference in which detail may be understood.