Defining the term "spell" in mastery trees.

There have been a lot of threads created by people wondering what, exactly, counts as a spell as far as the masteries are concerned. For some bizarre reason, no one at Riot has officially cleared this up, but for what it's worth, the LoL wiki seems to say it's essentially another word for "ability".

Here's a link to their offensive mastery page. If you hover over the mastery, the tooltip has a re-worded description that's more clear. If you go to the wiki-page for that mastery, the original wording is included.