labile

adjective

• Liable to slip, err, fall, or apostatize.
• Apt or likely to change.
• (of a compound or bond) Kinetically unstable; rapidly cleaved (and possibly reformed).

  "Certain drugs can be conjugated to polymer molecules with a linkage that is labile at low pH to effect controlled release in a cellular endosome."

• (of a verb) Able to change valency without changing its form; especially, able to be used both transitively and intransitively without changing its form.