•Tenacity now appears on the character sheet as a stat. ◦All champions with abilities that reduce the duration of disabling effects now gain tenacity instead. ■e.g. Singed, Trundle, Irelia, Garen, etc.

◦Champion tenacity stacks with item tenacity, mastery tenacity and cleanse.

Actually sir, mastery tenacity stacks Multiplicatively with in game tenacity from items. Tenacity got a major buff.

I don't believe anything was changed at all. I think it was just a change directed at cleaning up term usage in the game, whereas the effects stack the exact same way as before. I'm not 100%, but I'm pretty damn close to be sure.

Pretty sure it's just a tooltip cleanup; calling all CC reduction Tenacity to shorten the name.