Plurale tantum

Even a single item is called scissors (the singular form scissor is sometimes used in India)

A plurale tantum (Latin for 'plural only'; pl. pluralia tantum) is a noun that appears only in the plural form and does not have a singular variant for referring to a single object. In a less strict usage of the term, it can also refer to nouns whose singular form is rarely used.

'Putting on pants' is correct, 'putting on pant' sounds odd

In English, pluralia tantum are often words that denote objects that occur or function as pairs or sets, such as spectacles, trousers, pants, scissors, clothes, or genitals. Other examples are for collections that, like alms and feces, cannot conceivably be singular. Other examples include suds, jeans, outskirts, odds, riches, gallows, surroundings, thanks, and heroics.

In some languages, pluralia tantum refer to points or periods of time (for example, Latin kalendae 'calends, the first day of the month', German Ferien 'vacation, holiday'), or to events (for example, Finnish häät 'wedding'), or to liquids (for example, Hebrew מַיִם (mayim) and Chichewa madzí, both 'water').

A bilingual example is the Latin word fasces that was brought into English; when referring to the symbol of authority, it is a plurale tantum noun in both languages.[1]

  1. ^ Harper, Douglas. "fasces". Online Etymology Dictionary. "1590s, from Latin fasces 'bundle of rods containing an axe with the blade projecting' (plural of fascis 'bundle' of wood, etc.).... Carried before a lictor, a superior Roman magistrate, as a symbol of power over life and limb: the sticks symbolized punishment by whipping, the axe-head execution by beheading." Retrieved 2 August 2015.