mourn vs observe

mourn and observe both are verbs.

Word	Noun	Adjective	Verb	Adverb
mourn	No	No	Yes	No
observe	No	No	Yes	No

As verbs, observe is a hypernym of mourn; that is, observe is a word with a broader meaning than mourn:

Other hypernyms of mourn include celebrate, keep.

mourn (verb)	observe (verb)
feel sadness	stick to correctly or closely
observe the customs of mourning after the death of a loved one	make mention of
	watch attentively
	observe with care or pay close attention to
	discover or determine the existence, presence, or fact of by perception with the eyes
	follow with the eyes or the mind
	show respect towards
	behave as expected during of holidays or rites
	conform one's action or practice to