No-they do not expire. No US stamps issued since 1865 have been been devalued. The only exception are the special delivery stamps which paid for service no. longer offered. Air mail stamps are good for any purpose. Some stamps can't be used for certain things.
the pure and concentrated essence of a substance. 2. the most perfect embodiment of something. 3. (in ancient and medieval philosophy) the fifth essence or element, ether, supposed to be the constituent matter of the heavenly bodies, the others being air, fire, earth, and water. Origin of quintessence.
adherence noun [U]. âº the âfact of someone âbehaving âexactly âaccording to ârules, âbeliefs, etc.: He was ânoted for his âstrict adherence to the ârules. (Definition of adherence from the Cambridge Advanced Learnerâs Dictionary & Thesaurus Â© Cambridge University Press).ne area of particular interest to our users is that of English Language Teaching (ELT), and a number of ELT terms have recently been added to the dictionary.