phenomenon
Pronunciation: /fɪˈnɒmɪnən/
noun ( plural phenomena /-nə/)

Origin:
late 16th century: via late Latin from Greek phainomenon 'thing appearing to view', based on phainein 'to show'

The word phenomenon comes from Greek, and its plural form is phenomena, as in these phenomena are not fully understood. It is a mistake to treat phenomena as if it were a singular form, as in this is a strange phenomena.