of / əv/ • prep. 1. expressing the relationship between a part and a whole: the sleeve of his coat | in the back of the car the days of the week| a series of programs | a piece of cake a lot of money. 2. expressing the relationship between a scale or measure and a value: an increase of 5 percent a height of 10 feet. ∎  expressing an age: a boy of fifteen. 3. indicating an association between two entities, typically one of belonging: the son of a friend the government of India | a photograph of the bride | a former colleague of John's. ∎  expressing the relationship between an author, artist, or composer and their works collectively: the plays of Shakespeare the paintings of Rembrandt. 4. expressing the relationship between a direction and a point of reference: north of Chicago on the left of the picture. 5. expressing the relationship between a general category and the thing being specified which belongs to such a category: the city of Prague the idea of a just society the set of all genes. ∎  governed by a noun expressing the fact that a category is vague: this type of book the general kind of answer that would satisfy me. 6. indicating the relationship between a verb and an indirect object: ∎  with a verb expressing a mental state: they must be persuaded of the severity of the problem I don't know of anything that would be suitable. ∎  expressing a cause: he died of cancer. 7. indicating the material or substance constituting something: the house was built of bricks walls of stone. 8. expressing time in relation to the following hour: it would be just a quarter of three in New York.PHRASES: be of possess intrinsically; give rise to: this work is of great interest and value.of all denoting the least likely or expected example: Jordan, of all people, committed a flagrant foul.of all the nerve (or Brit. cheek) an expression of indignation.of an evening (or morning, etc.) inf. 1. on most evenings (or mornings, etc.). 2. at some time in the evenings (or mornings, etc.).