Open English Wordnet
Nouns
(n)incidental expense, incidental, minor expense(frequently plural) an expense not budgeted or not specified“he requested reimbursement of $7 for incidental expenses”
Adjectives
(a)incidental, incident(sometimes followed by ‘to’) minor or casual or subordinate in significance or nature or occurring as a chance concomitant or consequence“incidental expenses”, “the road will bring other incidental advantages”, “extra duties incidental to the job”, “labor problems incidental to a rapid expansion”, “confusion incidental to a quick change”
(s)incidental, nonessential, accidentalnot of prime or central importance“nonessential to the integral meanings of poetry” (Pubs.MLA), “the character's motives remain accidental to the plot”
(s)attendant, consequent, accompanying, concomitant, incidental, ensuant, resultant, sequent, collateraloccurring with or following as a consequence“an excessive growth of bureaucracy, with attendant problems”, “snags incidental to the changeover in management”, “attendant circumstances”, “the period of tension and consequent need for military preparedness”, “the ensuant response to his appeal”, “the resultant savings were considerable”, “collateral target damage from a bombing run”