Phenomenon

n. [pl. Phe-nōm'e-na. (Gr. φαινόμενον, from φαίνω, to appear; Lat. phænomenon, It. & Sp. fenomeno, Fr. phénomène.]

1. An appearance; any thing visible; whatever is presented to the eye; whatever, in matter or spirit, is apparent to, or is apprehended by, observation, as distinguished from its ground, substance, or unknown constitution; as, phenomena of heat or electricity; phenomena of imagination or memory.
2. Sometimes, a remarkable or unusual appearance, or an appearance whose cause is not immediately obvious.