Replaceable and Commutable

adjective

• Capable of being replaced. .

• (a.) Capable of being replaced (by) or of being exchanged (for); as, the hydrogen of acids is replaceable by metals or by basic radicals.
• (a.) Capable or admitting of being put back into a place.
• (a.) Admitting of having its place supplied by a like thing or an equivalent; as, the lost book is replaceable.

adjective

• Subject to alteration or change.
  • usage: "the death sentence was commutable to life imprisonment"
• Capable of being exchanged for another or for something else that is equivalent.
  • synonyms: substitutable