What is "entailment"

In logic, an entailment is the relationship between sentences whereby one sentence will be true if all the others are also true. Want a less-dry-sounding, real-life example? How about this: Being a good student, for instance, is an entailment of attending classes, learning the material, and keeping up with assignments. An old-fashioned definition of entailment is a set of limitations that restrict the ways property can be bequeathed to heirs.

Entailment is the process in which a property cannot be sold, devised by will, or otherwise done anything with by the owner. The property passes by law to the heir of the owner upon his death. Entailment was used to keep properties in the main line of succession.