Meaning of ACCIDENTAL in English
Casual, fortuitous, contingent, that happens by chance, not designed, not planned, unintended, chance, undesigned, not purposed.
Incidental, adventitious, non-essential, immaterial, dispensable, not absolutely requisite, de facto but not de jure , that has merely happened to be.
Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012