Legal drinking age. The legal drinking age is the age at which a person can legally consume or purchase alcoholic beverages. These laws cover a wide range of issues and behaviors, addressing when and where alcohol can be consumed.
An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept.
Open architecture. Not to be confused with Open-source architecture. Open architecture is a type of computer architecture or software architecture that is designed to make adding, upgrading and swapping components easy. For example, the IBM PC and Apple IIe have an open architecture supporting plug-in cards, whereas the Apple IIc and Amiga 500 computers have a closed architecture.