extend vs subclass

extend

verb
  • Of a class: to be an extension or subtype of, or to be based on, a prototype or a more abstract class. 

  • To reenlist for a further period. 

  • To increase in quantity by weakening or adulterating additions. 

  • To value, as lands taken by a writ of extent in satisfaction of a debt; to assign by writ of extent. 

  • To straighten (a limb). 

  • To increase in extent. 

  • To cause to increase in extent. 

  • To cause to last for a longer period of time. 

  • To possess a certain extent; to cover an amount of space. 

  • To bestow; to offer; to impart; to apply. 

subclass

verb
  • (in object-oriented programming) To create a subclass of (some class). 

  • To cause (an object) to act as an instance of a subclass (by creating the desired subclass and instantiating an object of this subclass). 

noun
  • A rank directly below class. 

  • A secondary class within a main class. 

  • An object class derived from another class (its superclass) from which it inherits a base set of properties and methods. 

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