The problem comes when the icon that it defaults to for printing is a right load, but the only way that envelopes can be loaded is in the center of the tray. I have an HP Colorlaserjet 3600 and an HP Officejet Pro 8600 and both load this way.
A technical definition of a function is: a relation from a set of inputs to a set of possible outputs where each input is related to exactly one output.
A function is a relation that uniquely associates members of one set with members of another set. More formally, a function from to is an object such that every is uniquely associated with an object. A function is therefore a many-to-one (or sometimes one-to-one) relation.