COMMUNICATIONS RETINAL CYSTS ANDRETINOSCHISIS* BY C. G. KEITH DepartmentofPathology, Institute ofOphthalmology, University ofLondon SINCE the term retinoschisis came into commonophthalmological parlance, it has oftenbeenusedas thoughthe conditionwereadefinite entity, differing fromretinal cysts bythe process byWhichit arose.
The definition of imperative is something that has authority or is absolutely necessary. 1  An example of imperative is the power that a government has over its people.  An example of imperative is the decision to give a cesarean in a breach birth.
In English grammar, an imperative sentence is a type of sentence that gives advice or instructions or that expresses a request or command. (Compare with sentences that make a statement, ask a question, or express an exclamation.) Also known as a directive or jussive. An imperative sentence typically begins with the base form of a verb, as in Go now!