'Sign' in the Bible

And Gehazi passed on before them, and laid the staff upon the face of the lad; but there was neither voice, nor sign of attention. And he returned to meet him, and told him saying, The lad is not awaked.

And this shall be the sign unto thee: They shall eat this year such as groweth of itself, And in the second year that which springeth of the same; But in the third year sow ye and reap, And plant vineyards and eat the fruit thereof.

And Hezekiah said to Isaiah, What shall be the sign that Jehovah will heal me, and that I shall go up into the house of Jehovah the third day?

And Isaiah said, This shall be the sign to thee from Jehovah, that Jehovah will do the thing that he hath spoken: shall the shadow go forward ten degrees, or go back ten degrees?