'Sign' in the Bible

And the Pharisees went out and began to dispute against him, seeking from him a sign from heaven, tempting him.

And groaning in his spirit, he says, Why does this generation seek a sign? Verily I say unto you, A sign shall in no wise be given to this generation.

Tell us, when shall these things be, and what is the sign when all these things are going to be fulfilled?

Now he that delivered him up had given them a sign between them, saying, Whomsoever I shall kiss, that is he; seize him, and lead him away safely.