The word pitṛ 'father' is optionally only retained when spoken of along with mātṛ 'mother'.,
Thus पिता + माता = पितरौ 'father and mother, or parents' or मातापितरौ. The verse quoted under sutra 1.2.68 illustrates this sutra also. There the word pitarau' has been explained by all commentators as \father and mother.\ The word \ekavad\ of the last sutra does not govern this sutra; though the anuvritti of 'optionally' is to be read into this.,