सुबामन्त्रिते पराङ्गवत् स्वरे

A word ending in सुप् or a case-affix, when followed by a word in the Vocative Case, is regarded as if it was the अङ्ग or component part of such subsequent vocative word, when a rule relating to accent is to be applied.
In other words, the word ending in a case-affix enters, as if, into the body of the vocative (ámantrita) word; as it will be taught in sútra 6.1.198 which declares 'a word ending in a vocative case-affix, gets the udátta accent on the beginning i.e. first syllable'. Now, this rule will apply even when a word ending with a case-affix precedes such word in the vocative case. Thus the word पती 'O two lords !' has udatta on the first syllable. Now, when this word is preceded by another inflected noun as शुभस् of prosperity, the accent will fall on शु, the two words being considered as a single word; as:-
अश्विना यज्वरीरिषो द्रवत्पाणी शुभस्पती | पुरुभुजाचनस्यतम || Rig. I.3.1.
"O Asvins, riding on quick horses, lords of prosperity, and bestowers of plenty of food, eat the sacrificial offerings to your satisfaction". So also in the following: कुण्डे नाटन् 'O thou wandering with a bowl'. परशुना वृश्चन् 'O thou cutting with an axe.' मद्राणां राजन् 'O thou king of Madras.' कश्मीराणां राजन् 'O thou king of Kashmir.'

Why do we say 'a word ending with a case-affix?' If the preceding word ends with any other affix than a case-affix, this rule will not apply. As a पीड्ये पीड्यमान 'O thou who art pained, I am pained because of this thy pain.'

Here पीड्ये 'being a तिङन्त (a verb)' is not considered as an anga of the vocative word.

Why do we say "when followed by a word in the vocative case ?" This rule will not apply when the subsequent word is not a vocative. As गेहे गार्ग्यः ' Gárga is at home.'

Why do we say 'of the subsequent?' It will not be a part of the vocative word which precedes. As देवदत्त कुण्डे नाटन् 'O Devadatta wandering with a bowl' Here कुण्डेन has not become part of Devadatta, but of the subsequent word अटन् .

Why do we say 'an anga or component part?' Both must be considered as one word for the application of the rule of accent, so that the first syllable of each word separately may not get the udátta.

Why do we say 'as if or वत्.' It is not altogether the body of the subsequent word; rules depending upon its own separate independent existence also take effect.

Thus rule 8.1.55 declares 'a word ending in the vocative case is not anudátta when it follows the word आम् there intervening a word between itself and आम्;' as, आम् कुण्डेन नाटन् ! Here kundena is considered a separate word for the purposes of Rule 8.1.55 and is said to intervene between आम् and the vocative word अटन् ।

Why do we say 'for the purposes of the application of rule of accent?' For the purposes of the application of any other rule, it will not be the anga of the subsequent word; as, कूपे सिञ्चन् 'O thou sprinkling in the well.' चर्म नमन्. Here had कूपे and चर्म been the angas of the subsequent words for all purposes, their स and न would have been changed into च and ण respectively by Rules 7.4.2 &c.

Vart:-When a word ending in a case-affix becomes, as if, the component part of the subsequent word, it becomes so even when there are several words in apposition with it which intervene between it and the vocative word ; because that, of itself, does not constitute want of immediate ness. Thus तीक्ष्णया सूच्या सीव्यन् 'O thou sewing with a sharp needle' तीक्ष्णेन परशुना वृश्चन् .

Vart:-Prohibition must be stated of indeclinable words. As उच्चैरधीयान 'O thou reading loudly. नीचैरधीयान.