What does A stand for?

What does A mean?

A	Advanced Academic & Science » Universities
A	American Governmental » Suppliers
A	April Miscellaneous » Months Abbreviations
A	America International
A	Against Academic & Science » Mathematics
A	Another Miscellaneous
A	Archives Business » General
A	Act Community » Performing Arts
A	Apple Miscellaneous » Food
A	Appropriate Miscellaneous
A	Art Academic & Science » Universities
A	Animals Medical » Veterinary
A	Accepted Business » Accounting
A	Atom Academic & Science » Chemistry
A	Australian Academic & Science » Geology
A	Actor Business » Positions
A	The Arts Academic & Science » Universities
A	Awesome Miscellaneous
A	Autos Governmental » Transportation
A	Ann Miscellaneous » Names and Nicknames
A	Ant Medical » Veterinary
A	Archived Computing » General
A	Activism Community
A	Ape Medical » Veterinary
A	Arte Miscellaneous » Names and Nicknames