RSVP PART is an acronym for the French phrase 'Repondez s'il vous plaît', which translates to 'please respond'. The crossword solutions PLAIT, VOUS, and SIL are all components of this phrase. PLAIT is the conjugated form of the verb 'plaire', meaning 'to please'. VOUS is the pronoun 'YOU' in the formal form. SIL is the pronoun 'he/she/it' in the third person singular form. Together, these three words make up the phrase 'Repondez s'il vous plaît', which is commonly used as a polite request for a response.