A short vowel is the substitute of prātipadika which ends with the word go 'a cow' and of that which ends with what has as its termination a feminine affix, when regarded as upasarjana,
The word upasarjana has been defined in sutra 1.2.43. In compounds the word गो becomes shortened when it stands last and is an upasarjana.
Thus चित्र + गो = चित्रगुः 'possessed of a brindled cow.' This is an example of a Bahuvrihi or possessive compound. So also शबलगु 'a spotted cow.' Similarly in those pratipadika upasarjanas which end in feminine suffixes having a final long vowel, there is a shortening. Thus निः + कौशाम्बी = निष्कौशाम्बिः. Here the final long ई is shortened. So also निर्वाराणसिः.
The word pratipadika of the previous sutra is understood in this. The word गो in the sutra means the form गो and not other words synonym with it. The word स्त्री means \a word ending in a feminine affix,\ because it has the svarita accent. The word upasarjana qualifies both these words, i. e. when गो is an upasarjana and when a word having a feminine termination is an upasarjana.
Other examples are:- अति + खट्वा = अतिखट्वः 'without a bed-stead' अतिमालः 'surpassing a necklace in beauty.'
If such a word is not an upasarjana, there is no shortening, as, राजकुमारी 'the king's daughter.' Here the word राजन् is upasarjana, and not the word कुमारी which latter is therefore not shortened. The word must be a derivative word formed by the addition of an affix, which makes it feminine. Thus the words लक्ष्मी, श्री &c. are feminine originally, and are not derived from the masculine nouns, by the addition of any feminine affix. Therefore we have अतिलक्ष्मीः 'surpassing Lakshmi in beauty', अतिश्रीः ॥
Vart :- In Bahuvrihi compounds, exception must be made of feminine nouns ending in the affix ईयसी, as बहुश्रेयसी, विद्यमानश्रेयसी ।,