philately   fuh-LAT-uh-lee   (noun)
     : the collection and study of postage and imprinted stamps
: stamp collecting


Example sentence:
     Mark's been interested in philately since he was a kid,
so he was thrilled to learn that a huge postage stamp exhibition
was coming to town.

Did you know?
     Who wouldn't love something tax free? George Herpin did.
He was a French stamp fancier back in the 1860s, when stamps
were a fairly new invention. Before stamps, the recipient of
a letter -- not the sender -- had to pay the postage. Stamps
forced the sender to foot the bill, and created a lot of stamp
lovers among folks on the receiving end of the mail -- and a
mania for stamp collecting. "Timbromania" was toyed with as a
term to affix to this new hobby -- from the French word for
stamp, "timbre." But when Herpin suggested "philatelie"
(anglicized to "philately"), combining the Greek root "phil-,"
meaning "loving," with Greek "ateleia," meaning "tax-exemption,"
stamp lovers everywhere took a fancy to it and the name stuck.