1. (adjective) not subject or susceptible to change or variation in form or quality or nature

• immutable

2. (adjective) unvarying in nature

• constant
• invariant
• unvarying

3. (adjective) remaining the same for indefinitely long times

• unalterable

1. (adjective) unvarying in nature

• invariable

2. (adjective) remaining the same for indefinitely long times

• unchangeable

1. (adjective) not subject or susceptible to change or variation in form or quality or nature

• changeable
• mutable

1. (adjective) not subject or susceptible to change or variation in form or quality or nature

• changelessness
• unchangeability
• unchangeableness
• unchangingness
• fixity
• fixity
• immutability
• immutability
• immutableness
• immutableness

2. (adjective) unvarying in nature

• changelessness
• constancy
• stability
• invariability
• invariableness
• invariance

3. (adjective) remaining the same for indefinitely long times

• changelessness
• unchangeability
• unchangeableness
• unchangingness
• fixedness
• unalterability
• unalterability