Substitutable and Changeable

adjective

• Of words. ( interchangeable in a given context without changing the import of the expression)
• Capable of being exchanged for another or for something else that is equivalent.
  • synonyms: commutable

adjective

• Capable of or tending to change in form or quality or nature.
  • usage: "a mutable substance"; "the mutable ways of fortune"; "mutable weather patterns"; "a mutable foreign policy"
  • synonyms: mutable
• Such that alteration is possible; having a marked tendency to change.
  • usage: "changeable behavior"; "changeable moods"; "changeable prices"
  • synonyms: changeful
• Subject to change.
  • usage: "a changeable climate"; "the weather is uncertain"; "unsettled weather with rain and hail and sunshine coming one right after the other"
  • synonyms: uncertain, unsettled
• Varying in color when seen in different lights or from different angles.
  • usage: "changeable taffeta"; "chatoyant (or shot) silk"; "a dragonfly hovered, vibrating and iridescent"
  • synonyms: chatoyant, iridescent, shot

• (a.) Appearing different, as in color, in different lights or under different circumstances; as, changeable silk.
• (a.) Capable of change; subject to alteration; mutable; variable; fickle; inconstant; as, a changeable humor.