IPA: /ˈrɪdʒ.ɪd.nəs/
KK: /ˈrɪdʒɪdnəs/
The quality of being stiff and not able to bend easily.
The rigidness of the metal made it difficult to shape into the desired form.
Rigidness → It is formed from "rigid" (from Latin "rigidus", meaning stiff or unyielding) and "-ness" (meaning the state or quality of). The word "rigidness" refers to the quality of being stiff or inflexible.
Think of the word 'rigid' which means stiff, and remember that 'rigidness' describes the state of being stiff or unyielding.