constant vs eternal

constant

adj
  • Unchanged through time or space; permanent. 

  • Firm; solid; not fluid. 

  • Steady in purpose, action, feeling, etc. 

  • Bounded above by a constant. 

  • Consistently recurring over time; persistent. 

noun
  • A quantity that remains at a fixed value throughout a given discussion. 

  • Any property of an experiment, determined numerically, that does not change under given circumstances. 

  • That which is permanent or invariable. 

  • An identifier that is bound to an invariant value; a fixed value given a name to aid in readability of source code. 

eternal

adj
  • existing outside time; as opposed to sempiternal, existing within time but everlastingly 

  • Lasting forever; unending. 

  • Constant; perpetual; ceaseless; ever-present. 

noun
  • One who lives forever; an immortal. 

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