'Generation' in the Bible

Then Yahweh said to Noah, "Go--you and all your household--into the ark, for I have seen you [are] righteous before me in this generation.

And the fourth generation shall return here, for the guilt of the Amorites {is not yet complete}."

And Joseph saw Ephraim's children to the third generation. Moreover, the children of Makir, son of Manasseh, were born on the knees of Joseph.