felicitación
/feliθitaˈθjon/ · B1 · noun · f
congratulation
🎉 feliz (happy) + -ación: the act of wishing someone happy
From Latin felix, happy, the same root as feliz and English felicity. Felicitar means to wish someone happiness, and -ación turns the verb into a noun, like English felicitation. Plural felicitaciones is what you say: congrats!