subtle

a.精巧的；机敏的；敏锐的，复杂的

substantial, substantially, substantiate, substantiation, substantive, substantively, substation, substitute, substitute for, substitute...for, substitution, substratum, substructure, subsume, subtenancy, subtenant, subtend, subterfuge, subterranean, subtitle, subtlety, subtly, subtopia, subtopic, subtotal, subtract, subtraction, subtropical, suburb, suburban, suburbanite, Suburbia, subvention, subversion, subversive, subversively, subversiveness, subvert, subway, subzero,