'Generation' in the Bible

And the LORD said unto Noah, Come thou and all thy house into the ark; for thee have I seen righteous before me in this generation.

But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.

And Joseph saw Ephraim's children of the third generation: the children also of Machir the son of Manasseh were brought up upon Joseph's knees.