'Generation' in the Bible

These are the generations of Noah. Noah was an upright man and without sin in his generation: he went in the ways of God.

And the Lord said to Noah, Take all your family and go into the ark, for you only in this generation have I seen to be upright.

And in the fourth generation they will come back here; for at present the sin of the Amorite is not full.

Every male among you, from one generation to another, is to undergo circumcision when he is eight days old, with every servant whose birth takes place in your house, or for whom you gave money to someone of another country, and not of your seed.

And Joseph saw Ephraim's children of the third generation: and the children of Machir, the son of Manasseh, came to birth on Joseph's knees.