'Generation' in the Bible

And sighing deeply in his spirit, he said, "Why does this generation demand a sign? Truly I say to you, no sign will be given to this generation!"

For whoever is ashamed of me and my words in this adulterous and sinful generation, the Son of Man will also be ashamed of him when he comes in the glory of his Father with the holy angels."

And he answered them [and] said, "O unbelieving generation! {How long} will I be with you? {How long} must I put up with you? Bring him to me!"

Truly I say to you that this generation will never pass away until all these [things] take place!