Table : Analytic expressions for effective polarizability α eff and extinction spectrum features (peak frequency ω res , peak height h, and linewidth W ) of Drude nanoparticles. Pair expressions are for truncation at the dipole level. Predictions from (D) MPM, the (E) mean-field approximation (i.e., Maxwell Garnett effective medium theory), and (F) the pairwise coupling approximation (see Table and Methods). The mean-field and pairwise coupling predictions in (E) and (F) qualitatively fail to describe the features of the MPM spectra in (D) due to neglect of interparticle correlations and many-body mutual polarization effects, respectively. Here, η = 0.00 represents the single-particle limit.