lettre de cachet vs cachet

lettre de cachet and cachet both are nouns.

Word	Noun	Adjective	Verb	Adverb
lettre de cachet	Yes	No	No	No
cachet	Yes	No	No	No

As nouns, lettre de cachet and cachet are synonyms defined as:

lettre de cachet and cachet: a warrant formerly issued by a French king who could warrant imprisonment or death in a signed letter under his seal

lettre de cachet (noun)	cachet (noun)
a warrant formerly issued by a French king who could warrant imprisonment or death in a signed letter under his seal	a seal on a letter
	an indication of approved or superior status
	a warrant formerly issued by a French king who could warrant imprisonment or death in a signed letter under his seal