Linguists have long classified languages according to the ways in which their intransitive subjects, transitive subjects, and direct objects align with respect to case marking and/or agreement. The two main divisions are known as the (nominative–)accusative and ergative(–absolutive) alignments. Under an accusative alignment pattern, the intransitive subject (abbreviated here as S) and the transitive subject (A: for agent, or agent-like argument) are encoded the same way (nominative), while the transitive direct object (O) is encoded separately (accusative). Under an ergative alignment pattern, on the other hand, S and O have identical encoding (absolutive) while A has its own separate case (ergative); see Comrie (1978); Dixon (1979; 1994); Manning (1996); Aldridge (2008); McGregor (2009); among others. These alignments can be expressed not only through case marking but also through agreement; S and A may determine the same agreement, in contrast to O, or S and O may license the same agreement, in contrast to A.