I wonder if there are many words that have quite opposite meanings? The noun 'sanction' (loosely) means a permission and a penalty; as a verb it means both 'to authorise' and 'to penalise'. I wonder whether this is rare - for the moment I can't think of any others, but I daresay that there are many examples.

Welcom Lucy, nice to see a new person on board.

This topic has been discussed several times, and at great length, in the past so you may not get many responses. If you click on the address below it will lead you to what I think is the first time it was brought up (you'll see that one of the responses is quite similar to your question).

http://wordsmith.org/board/showthreaded.pl?Cat=&Board=words&Number=443&page=&view=&sb=&vc=1#Post443

I know it may seem a little daunting, considering the quantity, but it can be interesting to go through a few of the back threads just to see what was going on. Or don't.

The most important part you have to remember...have fun!