allegation vs plaint

allegation and plaint both are nouns.

Word	Noun	Adjective	Verb	Adverb
allegation	Yes	No	No	No
plaint	Yes	No	No	No

As nouns, plaint is a hyponym of allegation; that is, plaint is a word with a more specific, narrower meaning than allegation:

allegation: (law) a formal accusation against somebody (often in a court of law)
plaint: (United Kingdom) a written statement of the grounds of complaint made to court of law asking for the grievance to be redressed

Other hyponyms of allegation include lodgement, lodging, lodgment, grievance.

allegation (noun)	plaint (noun)
(law) a formal accusation against somebody (often in a court of law)	a cry of sorrow and grief
statements affirming or denying certain matters of fact that you are prepared to prove	(United Kingdom) a written statement of the grounds of complaint made to court of law asking for the grievance to be redressed