A constituent part of the substance or aggregate; that part of a substance or an aggregate, which is incapable of being actually sundered (and hence is inalienable division of it); it is only an intellectual 'construct' which, on the basis of its utility, is an imaginary fragment of the whole.
vastuno'pṛthagbhūto buddhikalpitoṃ'śo deśa ucyate.
(jaisidī 1.30 Vṛ)