1. Inflexibleness.

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

• inflexibilty,
• inflexability,
• inflexibiltiy,
• infesibility,
• unflexibility,
• inflecibility,
• inflesibility,
• nflexibility,
• inflexiblity,
• inflexibillity,
• inflaxibility,
• reflexibillity,
• Unflexability,
• Unflexablity,
• Unflexiblility,
• Unflexibilty,
• Unflexiblity,
• inflexabillity,
• inflextibility,
• Intilegibility

• inflexible,
• inflexibleness,
• infallibility,
• inflexibly.

The adjective form of the word "inflexibility" is "inflexible".

The plural of the "inflexibility" can be the "inflexibilities".

The singular of the "inflexibility" can be the "inflexibility".