(linguistics) A system for writing one or more languages; a particular alphabetic, syllabic, logographic, or other scheme. For example, the Latin alphabet or the Cyrillic alphabet.

A refrigeration system that utilizes ammonia being absorbed by water, to create the cooling effect.

An arrangement whereby the main responsibility for welfare payments, especially unemployment benefits, is held by trade or labour unions rather than a government agency.

(mathematics) a set of equations required to be satisfied simultaneously or considered as a whole

(crystallography) Any of the seven distinct symmetry classifications of crystals: cubic, tetragonal, hexagonal, orthorhombic, monoclinic, triclinic and trigonal.

The system of measurements based on force, and independent of acceleration of gravity.

(astronomy) A geocentric model of the solar system, described by the eponymous astronomer.

(object-oriented programming) A concept for computer language types where a primitive type can support methods and encapsulation, but only reference types support virtual methods and specialization.

(rail transport) A rail system used in mountainous terrain with multiple cograils.

(Indo-European studies) A system which describes how certain Proto-Indo-European words are derived from one another.