a form of malaria that may be intermittent or remittent, consisting of a chill accompanied and followed by fever with its attendant general symptoms and terminating in a sweating stage; the paroxysms, caused by release of merozoites from infected cells, typically recur every 48 hours in tertian (malaria vivax or malaria ovale) malaria, every 72 hours in quartan (malariae) malaria, and at indefinite but frequent intervals, usually about 48 hours, in malignant tertian (falciparum) malaria, but in many cases periodicity is not well established.