The syllable an of a aṅga (stem) ending in an remains unchanged before a taddhita affix beginning with y when it does not denote existence in abstract of the avocation of someone.,
Thus सामसु साधुः = सामन्यः, ब्राह्मण्यः ॥ But राज्ञो भावः कर्म वा = राज्यम् ॥ राजन् belongs to Purohitadi class and takes यक् (V. I. 128).,