diary vs journal

diary and journal both are nouns.

Word	Noun	Adjective	Verb	Adverb
diary	Yes	No	No	No
journal	Yes	No	No	No

As nouns, journal is a hypernym of diary; that is, journal is a word with a broader meaning than diary:

As nouns, diary and journal are synonyms defined as:

diary and journal: a daily written record of (usually personal) experiences and observations

diary (noun)	journal (noun)
a personal journal (as a physical object)	the part of the axle contained by a bearing
a daily written record of (usually personal) experiences and observations	a record book as a physical object
	a periodical dedicated to a particular subject
	a daily written record of (usually personal) experiences and observations
	a ledger in which transactions have been recorded as they occurred