fixity
1. [ noun ] the quality of being incapable of mutation
Synonyms: immutableness immutability
Examples:

"Darwin challenged the fixity of species"

Related terms: mutability mutability changelessness agelessness unalterability
2. [ noun ] the quality of being fixed in place
Synonyms: fixedness secureness fixture fastness
Related terms: immovability lodgment fasten
Similar spelling:   fist
  fight