I cast a card with megamorph and state "I'll pay {3} and morph this." Is this particular method of communication for casting a face-down creature legal? The reason I ask is because morph and megamorph mean different things.
If I control a face down creature with megamorph, and my opponent asks if it was morphed or megamorphed, am I obligated to respond? If I'm not obligated to respond, but I choose to do so, am I obligated to respond truthfully?
I know that I have to distinguish between manifests and morphs. I'm just not sure if I have to distinguish between morphs and megamorphs. Nearly all of my opponents at my Dragons of Tarkir prerelease events just said "Morph this guy." and it turned out to be a megamorph (surprise!). Given the non-existence of regular morph cards in Dragons of Tarkir, I decided to not ask a judge because I knew they were really all megamorphs. I want to know in case I run into this later.