Synonyms of step by step

Adjective

1. bit-by-bit, in small stages, piecemeal, step-by-step, stepwise, gradual (vs. sudden)

usage: one thing at a time

Adverb

1. gradually, bit by bit, step by step

usage: in a gradual manner; "the snake moved gradually toward its victim"

2. stepwise, step by step

usage: proceeding in steps; "the voltage was increased stepwise"