A vector is a unit vector if its norm is 1.
Phrases are syntactical units.
The family is the fundamental unit of society.
This is an old unit.
To change the units from metric to imperial and vice versa, the 'menu' button must be clicked.
As soon as we are born, the world gets to work on us and transforms us from merely biological into social units.
At that moment, the telephone in the unit office rang.
1. section: piece, square, block, factor, joint, length, quantity
2. system: complement, element, component, member, part, total, assemblage