Here is MW Dic of Syn quoted by Nephew from Multitran
"Admittance" is mostly confined to the literal sense of allowing one to enter a locality or building
no admittance without a pass
admittance to the grounds
"Admission" has acquired the figurative sense of admitting to rights, privileges, standing, membership
his admission to the club
admission of new words into the language
When entrance into a building or a locality carries with it certain privileges, admission rather than admittance is used
admission to a theater
the admission of aliens into a country
http://books.google.com/books?id=8N4UReTJYhUC&pg=PA21&lpg=PA...
"no admittance without a pass"
"admission rather than admittance is used"
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