Pre-noun adjectival (rentaishi) used to emphasize that something is merely or only what follows. Often implies a small amount, short time, or trivial nature.
the principle of the thing; the way things work; the natural order of things
Etymology
Derived from the noun 物 (もの, 'thing') + the possessive particle の, literally 'of a thing'. The meaning shifted to 'a mere thing' and then to the pre-noun adjectival use.
