श्रोत्रियं श्छन्दो ऽधीते

The न् in श्रोत्रियन् is for the sake of accent. As श्रो꣡त्रियो ब्राह्मणः \a Brahmana learned in the Vedas\. The word श्रोत्रिय is either a condensed expression for the full sentence छन्दोऽधीते, referring to no particular base or affix. Or the word छन्दस् is replaced by श्रोत्र, and then is added the affix घन् ॥ But how do you form then छान्दसः, in the sense of छन्दोऽधीते, by adding the affix or अण् by 4.2.59 ? The present sutra is optional, the word वा of 5.2.77 being understood here: so that we have the form श्रोत्रियः also. Some say that श्रोत्रिय applies only to that person who has not only studied the Vedas but who acts upon its purport also, while छान्दस applies to a student in general, so one sutra does not debar the other, as they apply to different objects.,