premises

When referring to a logical proposition, the word is used in the singular "premise" to describe a single starting assumption. In this logical context, it is a standard countable noun that follows typical English pluralization rules.

When referring to a building or land, the word is used almost exclusively in the plural form "premises." Even when referring to a single building, the plural form is required. Using the singular "premise" to describe a physical location is a common error and is considered incorrect in standard English.