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incidental

/ɪnsɪˈdɛnt(ə)l/
adjective
1 Happening as a minor accompaniment to something else.
1.1 Occurring by chance in connection with something else.
2 incidental to - Happening as a result of (an activity)
noun
usually incidentals
An incidental expense, event, etc.

Origin
Early 17th century originally from medieval Latin incidentalis,
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The illustrations added to these definitions are incidental, in spite of their frequent use.