Any group which when present on benzene ring has electron withdrawing (−NO2−CN,−SO3H,−COOH,−Cl,−C6H5, etc) group decreases basicity of aniline, e.g. aniline is more basic than nitroaniline. Lone pair electrons are more delocalised in diphenylamine and triphenylamine, thus these are less basic than aniline. In benzylamine the electron pair present on nitrogen is not delocalised with the benzene ring hence it is more basic than aniline.