As part of his special theory of relativity, einstein saw mass as a form of

Hello, this is easy =)

Just remember E = MC^2

As part of his special theory of relativity, Einstein saw mass as a form of ENERGY.

Best regards

Energy

Explanation:

Special theory of relativity describes the behaviour of a particle when moving at relativistic speeds.

Part of this theory is the mass-energy equivalent principle:

E = mc^2

Where c is the speed of light.

This means mass can be converted to energy and energy can be converted to mass.

Thus, Einstein saw mass as a form of energy.