In philately (stamp collecting) a stamp condition dictates its value even more drastically than in coin collecting. A rare stamp with a tiny tear might be worth 10 percent of a pristine example.
Centering
Centering refers to how perfectly the printed design sits within the margins of the paper. A perfectly centered stamp with equal white margins on all four sides commands a massive premium.
Perforations
The holes punched between stamps to allow separation are called perforations. Collectors look for stamps with intact teeth. Missing or short teeth lower the grade significantly.
Gum Condition
For unused mint stamps, Mint Never Hinged (MNH) means the gum is perfect and untouched. Stamps previously mounted using hinge stickers are worth considerably less.
Cancellations
For used stamps a light neat cancellation that leaves the stamp design visible is highly preferred over a heavy smudged postmark.