noun (n)

• the quality or attribute of being firm and steadfast(noun.attribute)

  Synonym:
  stableness
  Antonym:
  instability, unstableness
  

  source: wordnet30
• a stable order (especially of society)(noun.state)

  Antonym:
  instability
  

  source: wordnet30
• the quality of being enduring and free from change or variation(noun.attribute)

  Synonym:
  constancy
  Antonym:
  changefulness, inconstancy
  

  source: wordnet30
• The state or quality of being stable, or firm; steadiness; firmness; strength to stand without being moved or overthrown; as, the stability of a structure; the stability of a throne or a constitution.(noun)

  source: webster1913