<p><strong>Adjective</strong></p><ul><li>of or relating to a function or functions: functional difficulties in the administration</li><li>capable of operating or functioning: When will the ventilating system be functional again?</li><li>having or serving a utilitarian purpose; capable of serving the purpose for which it was designed: functional architecture; a chair that is functional as well as decorative</li><li>(of a building or furnishing) constructed or made according to the principles of functionalism or primarily as a direct fulfillment of a material need</li><li>Medicine/Medical: without a known organic cause or structural change; a functional disorder</li><li>pertaining to an algebraic operation: a functional symbol</li><li>Linguistics: concerned with the communicative role of language rather than, in addition to, or as the framework for its formal structure</li></ul><p><strong>Noun</strong></p><ul><li>Mathematics: a function that has a domain whose elements are functions, sets, or the like, and that assumes numerical values</li></ul>