I think it would be extremely helpful to both Learners and those answering their questions if there were a glossary on Khan Academy for math terms.

When answering Questions in 6th grade math, I often find that Learners are not sure of the meaning of a term (such as "rational"), and it can be difficult or impossible to find the meaning on the Khan Academy website.  Example: I just paged through the first 10 pages of the search results for "rational" without finding anything in 6th grade or before that defined the term, even though it is used in the titles for several 6th grade math videos.

As I understand it, many Learners are using Khan Academy in situations (such as school) where they may not be able to access other websites to look things up, so having definitions findable within this website would make a huge difference. The glossary could have written definitions, links to existing videos/articles, or both.  Khan Academy could even ask for volunteers to submit suggestions and only need Khan Academy staff to review the finished project and publish it.

Please consider making the current courses and website functionality work better as a higher priority than expanding into new areas.