capacity vs mental age

capacity

noun
  • Mental ability; the power to learn 

  • A measure of such ability; volume 

  • The maximum amount that can be held 

  • Electrical capacitance. 

  • Legal authority (to make an arrest for example) 

  • The maximum that can be produced. 

  • The ability to hold, receive, or absorb 

  • The maximum that can be produced on a machine or in a facility or group. 

  • A role; the position in which one functions 

  • Capability; the ability to perform some task 

  • A faculty; the potential for growth and development 

adj
  • Filling the allotted space. 

mental age

noun
  • How old one appears to be based solely on mental ability and function. 

How often have the words capacity and mental age occurred in a corpus of books? (source: Google Ngram Viewer )