Foxing is a term used to describe the yellow-brown discoloration that appears on paper and other materials over time. The term "foxing" is derived from the word "fox" as it is believed that this discoloration resembles the fur of a fox. However, there are several other synonyms for the term 'foxing' that are used by enthusiasts of book restoration and paper conservation. These include the terms aging, browning, spotting, yellowing, staining, and discoloration. Different terminology may be preferred based on the context in which the foxing appears, as well as the cause and severity of the discoloration.