1. That monastic order, which is headed by a single Ācārya (preceptor).
ekācāryapraṇeyasādhusamūho gacchaḥ.
(TaBhā 9.24 Vṛ)
2. That major form of monastic organization, which is constituted of the (minor sections like) Kula (1), Gaṇa (1) and Saṅgha (2).
gacchaḥ sādhusamūharūpo......gacchagrahaṇena
kula-gaṇa-saṃgharūpo gacchaḥ.
(Bṛbhā 2865 Vṛ)