"casts a creature spell" vs "plays a creature spell"

[Sphinx]

Whats the difference between "casting" a creature spell (ie in ability of Opal Archangel) and "playing" it (Pure Reflection)?

[Nik]

i think casts is like when you play it from your hand and pay mana for it

plays also covers playing it like from elvish piper

[Void Elemental]

"Cast" is the term that replaced "play" with the 2010 rules update. Casting a spell is no different from playing one with the exception of wording.

Elvish Piper doesn't let you play, it puts a creature into play.