ancillary; incidental; accompanying
Describes something that is secondary, supplementary, or occurring as a byproduct of a main action or condition. Often used in formal or technical contexts.
This issue is merely incidental.
As an ancillary service, we offer free parking.
副次的 also means 'secondary' or 'subsidiary', but emphasizes a subordinate or less important role, while 付随的 focuses on something that naturally accompanies or is incidental to something else.
Derived from the noun 付随 (ふずい, 'accompaniment') + the adjectival suffix 的 (てき, '-like, -ic'). The kanji 付 means 'attach' and 随 means 'follow', together suggesting something that follows along with the main thing.