At a certain (often past) moment or period in time
एक समय पर
English Usage: "At one time, this house was a bustling inn."
Hindi Usage: "किसी समय पर, यह घर एक व्यस्त सराय हुआ करता था।"
kisi samay par, kisi samay pe, kisi samay par bhi, kisī samay par, kisi samay mai
