# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
U
ultraviolet (UV) radiation: A mid- to high-energy type of electromagnetic radiation emitted by the Sun.
umbra: A region of full shadow.
universal indicator: An indicator, containing a number of indicators, that changes colour depending on the pH of a solution.
universe: The entire span of space and time.