Double strike Rule 702.4 Glossary

A keyword ability that lets a creature deal its combat damage twice. See rule 702.4, “Double Strike.”
Prowess Rule 702.108 Glossary

A keyword ability that causes a creature to get +1/+1 whenever its controller casts a noncreature spell. See rule 702.108, “Prowess.”

Rulings (3)

September 20, 2014 Wizards of the Coast
Once it triggers, prowess isn’t connected to the spell that caused it to trigger. If that spell is countered, prowess will still resolve.
September 20, 2014 Wizards of the Coast
Any spell you cast that doesn’t have the type creature will cause prowess to trigger. If a spell has multiple types, and one of those types is creature (such as an artifact creature), casting it won’t cause prowess to trigger. Playing a land also won’t cause prowess to trigger.
September 20, 2014 Wizards of the Coast
Prowess goes on the stack on top of the spell that caused it to trigger. It will resolve before that spell.

Other Printings

Pioneer Masters (pio) Khans of Tarkir Promos (pktk)