obsesión
/obseˈsjon/ · B2 · noun · f
compulsion
Twin of English obsession; from Latin obsidere = to besiege
Spelled like the English word, but the double ss becomes a single s and -ion gets an accent: obsesión. Latin obsidere = ob (against) + sedere (sit): a thought that camps outside your walls like an army laying siege. It is feminine: la obsesión.