1. That may be proved.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• probables,
• proveable,
• profaile,
• probvably,
• proabley,
• provibe,
• propble,
• provale,
• probale,
• prbable,
• provail,
• prevaile,
• rmovable,
• peronable,
• propable,
• probible,
• promble,
• probabley,
• proble,
• profible

• probabilism,
• probably,
• probable,
• provability,
• provably,
• probability,
• prefab.

The adjective form of the word "provable" is "provable", as it is already an adjective.

The plural form of the word "provable" is "provables".

The singular form of the word "provable" is "provable".