These two words sound almost the same, and are different.
A plaintiff (demandante) is someone who goes to a court with a complaint. Two examples:
- Mr. Sanchez, the plaintiff, went to court (…el damandante, fue a juicio…) to silence Mr. Feijoo.
- The jury resolved the dispute in favour of the plaintiff (…a favor del demandante).
Mortals can be plaintive, that is, sounding or looking sad or sorrowful (afligado/triste). Two examples:
- You have a plaintive look today (…una cara lastimera hoy).
- Mr. Sanchez said goodbye to Mr. Johnson in a plaintive voice (…una voz lastimera).
Perhaps you have been a plaintiff and in the court – or another place – you had a plaintive face. Who knows?