The affix ṭhak comes in the sense of 'this is his act, occurring in study' after a word in the Nominative 1st-Case in construction, if such a word is an karma (act) which has vṛttam (occurred) adhyayana in (study).,
Thus एकमन्यदध्ययने कर्मवृत्तमस्य = ऐकान्यिकः 'a pupil who commits one (एक) error (अन्यत्) in reading', &c. literal translation being something like \one errorist\. Similarly द्वैयन्यिकः त्रैयन्यिकः &c. He whose, in recitation, at the time of examination, there is the occurrence of one mistake or false reading, is called ऐकान्यिकः ॥ So who commits two mistakes is called द्वैयन्यिकः ॥ In short, in giving explanatory analysis of taddhita words like ऐकान्तिकः &c, the whole phrase अध्ययने कर्मवृत्तम् must be employed.,