: not changing or capable of change : staying the same : not variable.

What does invariable mean in science?

not variable; not changing or capable of being changed; static or constant.

What does it mean when someone is invalid?

1 : affected by disease or disability : sickly. 2 : of, relating to, or suited to one that is sick an invalid chair. Other Words from invalid Synonyms & Antonyms Example Sentences Learn More About invalid.