The University and College Union (UCU) is a British trade union in further and higher education representing over 120,000 academics and support staff. UCU is a vertical union representing casualised researchers and teaching staff, "permanent" lecturers and academic related professional services staff. Definitions of all these categories are currently rather ambiguous due to recent changes in fixed term and open-ended contract law. In many universities, casualised academics form the largest category of staff and UCU members.