grievous vs serious

grievous and serious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
grievous	No	Yes	No	No
serious	No	Yes	No	No

As adjectives, grievous and serious are synonyms defined as:

Other synonyms of grievous include dangerous, grave, life-threatening, severe.

grievous (adjective)	serious (adjective)
causing fear or anxiety by threatening great harm	concerned with work or important matters rather than play or trivialities
shockingly brutal or cruel	completely lacking in playfulness
of great gravity or crucial import; requiring serious thought	causing fear or anxiety by threatening great harm
causing or marked by grief or anguish	requiring effort or concentration; complex and not easy to answer or solve
	of great consequence
	appealing to the mind