treacherous vs perfidious

treacherous and perfidious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
treacherous	No	Yes	No	No
perfidious	No	Yes	No	No

As adjectives, treacherous and perfidious are synonyms defined as:

treacherous and perfidious: tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans

Other synonyms of treacherous include punic.

treacherous (adjective)	perfidious (adjective)
dangerously unstable and unpredictable	tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans
tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans