The word pati is called ghi only when it is in a compound.,
The word pati would have been ghi by the last sutra; the present sutra is therefore a niyama rule, restricting the use of ghi in the case of pati to its occurring in composition. The word eva 'only' is used in a restrictive sense.
As पत्या by the lord but प्रजापतिना by the lord of creatures. So also पत्ये and प्रजापतये; पत्युः and प्रजापतेः, पत्यौ and प्रजापतौ &c. When पति is ghi, there is guna of the vowel before the four ङित् affixes by 7.3.111.,