The U S Postal Service class of mail that provides the most timely delivery and is therefore the most expensive class, outside of express service Occasionally, a direct mailer will choose to use first class for speed or impact purposes, instead of the usual Standard A service class Invoices must be sent first class or attached to a magazine issue (see “Attached Renewal/Invoice”) The BRE and BRC are also first class return mail
nicest and most expensive passenger section (in a plane, train, etc.); of the best quality, highest group in a classification; superior, choice, excellent
Top quality seats or services Generally, first-class service is the best (and the most expensive) the supplier has to offer However, some vendors offer an even more expensive "luxury class" (qv)
Dependable choices for both comfort and amenities Normally well located with good public areas Most will offer extra services such as 24 hour room service and air-conditioning
For personal mailers, this is "the" class of mail at the post office First class is often too expensive for bulk mailers, but invoices are sent first class
A language supports some data type as first-class when the objects of the type can be created and used as data at run time First-class data can be kept in variables, and passed to and returned from functions In dynamically typed languages, first-class data can also have its type examined at run-time
The U S Postal Service class of mail that provides the most timely delivery and is therefore the most expensive class, outside the express service Occasionally, a direct mailer will choose to use first class for speed or impact purposes, instead of the usual standard service class By law, invoices must be sent first class
the most expensive accommodations on a ship or train or plane the highest rank in a classification mail that includes letters and postcards and packages sealed against inspection