The semivowel र r, in making combinations with other consonants, is treated in a wholly peculiar manner, analogous with that in which the vowels are treated.
a. If pronounced before another consonant or combination of consonants, it is written above the latter, with a hook opening to the right (much like the sign of the vowel ṛ, as written under a consonant: 10 e): thus, र्क rka, र्ष rṣa, र्त्व rtva, र्म्य rmya, र्त्स्न rtsna.
b. Then, if a consonant-group thus containing r as first member is followed by a vowel that has its sign, or a part of its sign, or its sign of nasality (anusvāra: 70, 71), written above the line, the r-sign is placed furthest to the right: thus, र्के rke, र्कं rkaṅ, र्कि rki, र्की rkī, र्को rko, र्कीं rkīṅ, र्कों rkoṅ.
c. If r is pronounced after another consonant, whether before a vowel or before yet another consonant, it is written with a straight stroke below, slanting to the left: thus, प्रpra, ध्र dhra, ग्र gra, स्र sra,
ddhra, न्त्र ntra,
grya,
srva, न्त्र्य ntrya; and, with modifications of a preceding consonant-sign like those noticed above (13), त्रtra, द्र dra, श्र çra, ह्र hra.
d. When र r is to be combined with a following ऋ ṛ, it is the vowel which is written in full, with its initial character, and the consonant in subordination to it: thus,
rṛ.