Of  prep. Expressing: 1 origin or cause (paintings of turner; died of cancer). 2 material or substance (house of cards; built of bricks). 3 belonging or connection (thing of the past; articles of clothing; head of the business). 4 identity or close relation (city of rome; a pound of apples; a fool of a man). 5 removal or separation (north of the city; got rid of them; robbed us of £1000). 6 reference or direction (beware of the dog; suspected of lying; very good of you; short of money). 7 objective relation (love of music; in search of peace). 8 partition, classification, or inclusion (no more of that; part of the story; this sort of book). 9 description, quality, or condition (the hour of prayer; person of tact; girl of ten; on the point of leaving). 10 us time in relation to the following hour (a quarter of three).  be of possess, give rise to (is of great interest). Of an evening (or morning etc.) Colloq. 1 on most evenings (or mornings etc.). 2 at some time in the evenings (or mornings etc.). Of late recently. Of old formerly. [old english]