俱舍論記 1.266

1.266

「又為差別至獨名為法」者，別解法處。又為差別餘十一處立一法處名，非於一切十一處。雖標總稱，即受別名，如色應知。應有問言：何故餘十一處不立通名，唯標法處？故復釋言。以法處中，攝多法處故、攝增上法故，故立通名。餘處不爾。

Regarding [the text from] “Furthermore, for the sake of distinction …” to “… is solely called dharma,” this specifically explains the dharma-āyatana. Furthermore, to distinguish the other eleven āyatanas, the single name of dharma-āyatana is established, not for all eleven āyatanas. Although marked with a general title, it receives a specific name, just as should be known for form. There might be a question: Why do the other eleven āyatanas not establish the general name, and only [this one] is designated dharma-āyatana? Therefore it explains again: Because within the dharma-āyatana it subsumes many dharma-āyatanas and subsumes predominant dharmas, it is therefore established with the general name. The other āyatanas are not like this.