Sentence:  Both Cauchy and Abel must have been aware that <WSD>epsilontics</WSD> is a general tool for making rigorous proofs in analysis, but neither of them, to say nothing of their contemporaries, used it consistently. 
Meaning of the word marked with <WSD> tags:  An approach to mathematical analysis using the epsilon-delta definition of a limit, i.e. with explicit estimation of error bounds, as opposed to using infinitesimals.