menstrual cycle vs menstrual phase

menstrual cycle and menstrual phase both are nouns.

Word	Noun	Adjective	Verb	Adverb
menstrual cycle	Yes	No	No	No
menstrual phase	Yes	No	No	No

menstrual cycle (noun)	menstrual phase (noun)
a recurring cycle (beginning at menarche and ending at menopause) in which the endometrial lining of the uterus prepares for pregnancy; if pregnancy does not occur the lining is shed at menstruation	the phase of the menstrual cycle during which the lining of the uterus is shed (the first day of menstrual flow is considered day 1 of the menstrual cycle)