The process of figuring out exactly how much something is worth is known as valuation. Before you sell your old Pokemon cards, you should take them to an expert for a valuation.
Whenever you determine the monetary value of something, that's valuation. However, you're most likely to come across this word in the context of banking or finance. The valuation of a company affects whether or not investors are interested in it, and the valuation of stocks determines how much a stockholder makes when she sells them. Valuation shares a root with value, from the Latin root valere, "be strong, be worth."