stable1
Pronunciation: /ˈsteɪb(ə)l/
adjective ( stabler, stablest)
- (of an object or structure) not likely to give way or overturn; firmly fixed: specially designed dinghies that are very stable
- (of a patient or their medical condition) not deteriorating in health after an injury or operation: he is now in a stable condition in hospital
- sane and sensible; not easily upset or disturbed: the officer concerned is mentally and emotionally stable
- not likely to change or fail; firmly established: a stable relationship prices have remained relatively stable
- not liable to undergo chemical decomposition, radioactive decay, or other physical change: isocyanic acid reacts with amino groups to form a stable compound stable nuclei

Origin:
Middle English: from Anglo-Norman French, from Latin stabilis, from the base of stare 'to stand'