The synonyms permeable and pervious both make good use of the Latin prefix per-, meaning "through." Permeable traces back to a combination of per- and the Latin verb meare, meaning "to go" or "to pass," whereas the history of pervious calls upon Latin via, meaning "way." Both permeable and its more common relative, the verb permeate, still retain the original Latin idea of "passing through." Pervious also has the connotation of "penetrating through" but is also used to describe a susceptible mind, as in "Though set in his ways, the professor was pervious to reason." The prefix per- also gave English pervade, meaning "to become diffused throughout every part of." Meare also has other English descendants, including congé, which can mean "a formal permission to depart," and irremeable, meaning "offering no possibility of return."