n.
   - a person using the services of a professional person or organization.
 - (in a network) a computer or workstation that obtains information and applications from a server. 
▸
(also client application or program)
 a computer program that obtains a service provided by another program.
 - (in ancient Rome) a plebeian under the protection of a patrician. 
▸archaic a dependant; a hanger-on.
 
 
  Derivative
  
  Etymology
  ME (orig. denoting a person under the protection and patronage of another): from L. cliens, client-, var. of cluent-, cluere ‘hear or obey’.