phase: [19] Greek phásis (a derivative of the verb phaínein ‘show’, source of English phantom) meant ‘appearance’, and also ‘cyclical apparent form of a planet, moon, etc’. This was adopted into modern Latin as phasis, and it originally passed into English (in the 17th century) in the Latin plural form phases. Phase represents a new singular formed from this. The more familiar modern sense ‘stage in a sequence’ is a metaphorical extension of the astronomical meaning. => phantom[phase etymology, phase origin, 英语词源]