class period vs course session

class period and course session both are nouns.

Word	Noun	Adjective	Verb	Adverb
class period	Yes	No	No	No
course session	Yes	No	No	No

As nouns, class period and course session are synonyms defined as:

class period and course session: a regularly scheduled session as part of a course of study

Other synonyms of class period include recitation.

class period (noun)	course session (noun)
a regularly scheduled session as part of a course of study	a regularly scheduled session as part of a course of study