An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The precise time at which the gamma burst photons hit a detector. Measuring the time difference between the arrival time of the photons at different telescopes separated by known distances permits to determine the burst direction.

Arrival, n. from arrive + → -al. Arrive, from O.Fr. ariver "to come to land," from V.L. *arripare "to touch the shore," from L. ad ripam "to the shore," from → ad "to" + ripa "shore;" → time.

Zamân, → time; raseš n. from rasidan "to arrive," Mid.Pers. rasitan, O.Pers./Av. rasa- present stem of ar- "to move, go or come toward," cf. Skt. ar-, rcchati.

1) A person who is competing for the same object or goal as another, or who tries to equal or outdo another; competitor.
2) A person or thing that is in a position to dispute another's preeminence or superiority (Dictionary.com).

From L. rivalis "a rival, adversary; neighbor," originally, "one who uses a stream in common with another," from riv(us) "stream, brook," + -alis, → -al.

Hamâvard "a rival; an adversary in a combat," from ham- "together," → com-, + âvard "battle, struggle," variants nabard, nibard, nâvard "fight, struggle, war," ultimately from Proto-Ir. *part- "to fight, to struggle."

1) The action, position, or relation of a rival or rivals; competition.
2) An instance of this (Dictionary.com).

Noun from → rival.