A dvanda compound of words of different genders, denoting names of rivers and countries, but not of towns, is singular.,
Thus गंगाशोणम् 'the Ganges and the Sona. कुरवः + कुरुक्षेत्रं = कुरुकुरुक्षेत्रं 'the country of the Kurus and the Kurukshetra.' उद्ध्यैरावती कुरुकुरु जाङ्गलम् ॥
Why do we say 'of different genders'? Observe गंगायमुने 'the Gangas or and the Yamuna.' Both being feminine gender, so also मद्रकेकयाः ॥
Why do we say 'rivers and countries'? Observe कुक्कुटमयुर्यौ 'the hen and the pea-hen.'
Why do we say 'not of a town'? See जाम्बबशालूकिन्यौ 'Jambaba and Salukini, which are the names of two villages or grama.
We have taken the word 'river,' as the word 'country' does not include 'river.' So also 'mountains' are not included; as कैलासगन्धमादने 'the Kailasa and the Gandbamadana.'
Vart:- The prohibition extends to villages and towns (grama) but not to cities, (Nagara), as मथुरापाटलिपुत्रं 'the cities of Mathura and Pataliputra.'
Vart:- When a compound consists of two words, one a town and the other a city, the prohibition applies; as सौर्यकेतवते 'the city of Saurya and the village of Ketavata.',