What's the terminology difference between Tapas-austerities and Yajna-sacrifice/perseverance?

Also when to choose one over the other?

  • Tapas is shunning the desires which takes away from the truth. And Yajna is a spiritual practice which takes us closer to the truth. Yajna is positive counterpart of Tapas IMO. – Mr. Sigma. Feb 17 '18 at 16:03