n.
    - an individual thing or person regarded as single and complete but also able to form a individual component of a larger whole. 
▸a self-contained section of a building or group of buildings.
 ▸a subdivision of a larger military grouping.
 ▸a self-contained part of an educational course.
 ▸a single manufactured item.
 - a device or part with a specified function.
 - a standard quantity in terms of which other quantities may be expressed.
 - one as a number or quantity.
 
 
  Derivative
  
  Etymology
  C16: from L. unus, prob. suggested by digit.