Set is used for complete sets of equipment, such as desks, departments and instrument sets.
Unit: unit.
A tube of toothpaste, toothpaste tube.
A bundle: a group.
Units refer to organs, organizations or departments subordinate to organs and organizations; Refers to the name of the standard quantity for measuring things in mathematics or physics. Generally, there are: meters (m), kilometers (km), cattle (ton) N, pa (ska) PA and other units; In the traditional sense of Buddhism, units refer to quantitative units such as length, quality and time. And there are special terms such as: moment, moment, snap of fingers, moment and so on. Accurately speaking, a unit is a group of a certain amount of substances defined as "1" to become a unit.
Broadly speaking, unit is a relative concept and an abstract concept, which can form an individual on the coordinate axis of the object coordinate system. The smallest unit of things is zero.
Source: Baidu Encyclopedia: Unit