IPA: /ˌpɒlɪˈfeɪsɪk/
KK: /pɑˈlɪfeɪsɪk/
Describing something that has more than one phase or stage occurring at the same time or in succession.
The polyphasic sleep schedule allows for multiple short naps throughout the day instead of one long sleep at night.
Polyphasic → It is formed from "poly-" (from Greek "polus", meaning many) and "phasic" (from Greek "phasis", meaning phase or state). The word describes a state involving many phases, particularly in relation to sleep patterns.
Think of 'many' ('poly-') phases ('phasic') to remember that 'polyphasic' refers to having multiple phases, especially in sleep.
No commonly confused words.