Happening by chance; not planned.

संयोगिक

English Usage: Their meeting was purely coincidental.

Hindi Usage: उनकी मुलाकात पूरी तरह से संयोगिक थी।

A situation where events occur at the same time by chance.

संयोग

English Usage: The coincidental timing of their arrivals surprised everyone.

Hindi Usage: उनकी आगमन का संयोग सभी को चौंका दिया।