The noun patriarch means 'the [male] ruler (originally of a family or clan)'. (The word comes from the Greek πατριάρχης (patriarches), which means father or chief of a race, and is a compound of the two words πατριά (patria ( Latin for 'fatherland') meaning lineage or clan - a derivative of πατήρ 'father' (cognate of Latin pater, father) - and -αρχης‚ (arches, leader or chief).)
In everyday modern usage, it usually refers to a man who has - and visibly exerts - authority over a domestic situation, a family, extended family, household or similar group. It is also sometimes used to mean simply 'an old man' - 'the oldest man in the village' - or a person of long standing in a profession or craft, a doyen. In modern Christian usage, Patriarch is also a title borne by certain Bishops and their equivalents in some churches, notably in Eastern Orthodoxy, Oriental Orthodoxy, and the Assyrian Church of the East. In these, the term equivalent to the western 'bishopric' (the area of jurisdiction of a Bishop) is patriarchate. In the Roman Catholic Church, it is an honorific, ranking above Major Archbishop and primate, borne by the Latin Archbishop of Jerusalem; the Patriarch of the East Indies, or Archbishop of Goa and Daman; the Archbishop of Lisbon; and the Bishop of Venice. Historically, there have been others, including Antioch, Alexandria, Carthage and Constantinople.
In the Old Testament, it refers to the founders of the Jewish faith, Abraham, Isaac and Jacob. Less commonly nowadays, the twelve sons of Isaac, who founded the twelve tribes of Israel, are also called patriarchs. The period in which these fifteen lived is known as 'The Age of the Patriarchs'. In some uses, patriarch is also applied to Adam and his male descendants, down to the Flood. These, ending with Noah, are the antediluvian patriarchs.
The adjective patriarchal can refer to any of the noun meanings above. In addition, it is used in Sociology and Anthropology to describe social organizations in which males are dominant, in which fathers have authority over families, and so on. It is also used by feminists to characterize types of male behaviour against which women struggle, as in 'patriarchal hegemony'.