My pastor made this good statement tonight:

Teachers, and especially pastors, need to so understand great truths and subjects that they can explain it in different ways with different words.

So often we think we really something if we can spit out the same definition that we were taught.  But, the true test of whether or not we really know something is if we can explain it differently than we were taught it.  This shows a true level of comprehension.  Pastors especially need to have this ability in light of the seriousness of the truths they are responsible to teach.