thin, distributed, spaced out, frequent, equispaced, dotted, paucispicular, angustiseptate, hyperdispersed, brachysyllabic, more...

dense, thick, compact, concentrated, crowded

sparse matrix, sparse graph, sparse vector, sparse tensor, more...

little, rime, large, few, more, multicast, pagine, general, best, orbital, present

almost empty,   less dense,   not dense,   nearly empty,   few people,   thinly distributed,   thinly spread,   less populated,   thinly populated,   not very crowded