progressive

Progressive means advancing in stages, or in favour of reform. A progressive illness, progressive taxation, progressive politics.

Of an illness it means steadily worsening, which is a neutral clinical description. Of tax it means the rate rising with income, against regressive. Of politics it means favouring social reform, and it is a label people apply to themselves rather than to opponents. In grammar, the progressive is the -ing form. In music, progressive rock is a genre. Note progress, progression; and that progressive lenses are varifocals.