'Certain' in the Bible

Even as the witness of the Christ has been made certain among you:

And I gave baptism to the house of Stephanas; but I am not certain that any others had baptism from me.

Even to this hour we are without food, drink, and clothing, we are given blows and have no certain resting-place;

Is it not certain that the saints will be the judges of the world? if then the world will be judged by you, are you unable to give a decision about the smallest things?

Is it not certain that we are to be the judges of angels? how much more then of the things of this life?

For how may you be certain, O wife, that you will not be the cause of salvation to your husband? or you, O husband, that you may not do the same for your wife?

So, then, as to the question of taking food offered to images, we are certain that an image is nothing in the world, and that there is no God but one.

Even things without life, having a voice, such as a music-pipe or other instrument, if they do not give out different sounds, who may be certain what is being played?

For this cause, my dear brothers, be strong in purpose and unmoved, ever giving yourselves to the work of the Lord, because you are certain that your work is not without effect in the Lord.