unit

This term is defined in ECSS-E-ST-31C as
finished product with a given internal design

This term is defined in ECSS-E-ST-50-12C as
box, board or subsystem, that can have one or more SpaceWire interfaces

This term is defined in ECSS-E-ST-20-07C Rev. 1 as
equipment that is viewed as an entity for purposes of analysis, manufacturing, maintenance, or record keeping

This term is defined in ECSS-S-ST-00-01C as
see equipment