What is knowledge according to St. Thomas Aquinas?

The closest answer to your question would be this statement regarding knowledge:

Hence we must say that for the knowledge of any truth whatsoever man needs divine help, that the intellect may be moved by God to its act. But he does not need a new light added to his natural light, in order to know the truth in all things, but only in some that surpasses his natural knowledge.~ St. Thomas Aquinas