ό, τι means the same as οτιδήποτε (= anything, whatever thing ) For example: Πάρε ό,τι θέλεις. (=Take whatever you want.) Θέλω ό,τι θες εσύ. (I want what/whatever you want.) However, οτιδήποτε(which is the same) can be used alone as an answer, while ό, τι can not. For example: Τι θέλει; (=What does he want?) Οτιδήποτε. (= Anything, whatever thing) But watch out, because ό,τι with comma is different from ότι (without a comma) Ότι without comma means ''that'' . For example: Πιστεύω ότι θα έρθει. (I believe that he will come.) They are pronounced exactly the same ;) Are you learning greek? I'm from Greece so if you need any help don't hesitate to say so! I'd love to help.