Another useful limit to consider involves the number of sites N . In the case of molecular sites interacting with a cavity, N is usually in the order of 10 6 ; for more strongly coupled systems such as nanoparticles or nanoplatelets, N would be in the order of 10 3 . These cases correspond to the limit of N → ∞, hereon referred to as the collective limit. More specifically, this refers to the limit where the light-matter coupling has a predominantly collective nature, i.e., the individual coupling g c is weak such that the Rabi splitting Ω R = 2 √ N g c is large due to the large N .