199. In external combination, a final t

In external combination—

a. A final t is directed to be assimilated to an initial lingual mute: thus, taṭ-ṭīkā, taḍ ḍayate, taṭ-ṭhālinī, taḍ ḍhāukate: but the case never occurs in the older language, and very rarely in the later. For final n before a lingual, see 205 b.

b. An initial dental after a final lingual usually remains unchanged; and su of the loc. pl. follows the same rule: thus, ṣáṭtriṅçat, ā́naḍ diváḥ, ekarā́ṭ tvám; ṣaṭsú, rāṭsú.

c. Exceptions are: a few compounds with ṣaṣ six showing double ṇ (198 b): namely, ṣáṇṇavati, ṣaṇṇābhi (and one or two others not quotable): IB. has ṣaṇ ṇiramimīta.

d. In a few compounds, moreover, there appears a lingualized dental, with compensatory lengthening, after a lost lingual sibilant or its representative: namely, in certain Vedic compounds with dus: dūḍábha, dūḍā́ç, dūḍhī́, dūṇáça, dūṇā́ça (compare the anomalous puroḍā́ç and -ḍā́ça: puras + √dāç); and, in the language of every period, certain compounds of ṣaṣ, with change of its vowel to an alterant quality (as in voḍhum and soḍhum: 224 b): ṣóḍaça, ṣoḍhā́ (also ṣaḍḍhā́ and ṣaḍdhā́), ṣoḍant.

e. Between final ṭ and initial s, the insertion of a t is permitted—or, according to some authorities, required: thus, ṣáṭ sahásrāḥ or ṣáṭt sahásrāḥ.