The Book of Genesis (from the Latin Vulgate, in turn borrowed or transliterated from Greek "γένεσις", meaning "Origin"; Hebrew: בְּרֵאשִׁית, "Bərēšīṯ", "In [the] beginning") is the first book of the Hebrew Bible (the Tanakh) and the Old Testament. It is divisible into two parts, the Primeval history (chapters 1–11) and the Ancestral history (chapters 12–50). The primeval history sets out the author's (or authors') concepts of the nature of the deity and of humankind's relationship with its maker: God creates a world which is good and fit for mankind, but when man corrupts it with sin God decides to destroy his creation, saving only the righteous Noah to reestablish the relationship between man and God. The Ancestral History (chapters 12–50) tells of the prehistory of Israel, God's chosen people. At God's command Noah's descendant Abraham journeys from his home into the God-given land of Canaan, where he dwells as a sojourner, as does his son Isaac and his grandson Jacob. Jacob's name is changed to Israel, and through the agency of his son Joseph, the children of Israel descend into Egypt, 70 people in all with their households, and God promises them a future of greatness. Genesis ends with Israel in Egypt, ready for the coming of Moses and the Exodus. The narrative is punctuated by a series of covenants with God, successively narrowing in scope from all mankind (the covenant with Noah) to a special relationship with one people alone (Abraham and his descendants through Isaac and Jacob).
Genesis appears to be structured around the recurring phrase elleh toledot, meaning "these are the generations," with the first use of the phrase referring to the "generations of heaven and earth" and the remainder marking individuals—Noah, the "sons of Noah", Shem, etc., down to Jacob. It is not clear, however, what this meant to the original authors, and most modern commentators divide it into two parts based on subject matter, a "primeval history" (chapters 1–11) and a "patriarchal history" (chapters 12–50).[note 1] While the first is far shorter than the second, it sets out the basic themes and provides an interpretive key for understanding the entire book. The "primeval history" has a symmetrical structure hinging on chapters 6–9, the flood story, with the events before the flood mirrored by the events after; the "ancestral history" is structured around the three patriarchs Abraham, Jacob and Joseph. (The stories of Isaac do not make up a coherent cycle of stories and function as a bridge between the cycles of Abraham and Jacob).