Tagalog pronouns are divided into 3 categories: direct, indirect, oblique. Ako and ikaw/ka together with siya, fall under the Direct (singular). It marks the subject as the focus of the conversation. Nagbato ikaw/ka ng ballpen. = You tossed a ballpen. --> the focus is on "You" Ako ay si Green. = I am Green. --> the focus is on "I" me. Ko and mo together with niya, are under the Indirect (singular). It's a marker shifting the focus on the object instead. Binato mo yung ballpen. = You tossed the ballpen. --> the focus shifts on the ballpen itself. Sinalo ko yung ballpen. = I catched the ballpen. Iyo like akin and kaniya/kanya is under the Oblique (singular). It must be preceded by the place marker SA to indicate a beneficiary of an action. Binato mo yung ballpen sa akin. = You tossed the ballpen to me. --> I used "akin" (and not ako) to denote that I am the beneficiary of the action. Of course it must be preceded by "sa". Other examples: Regalo ko para sa iyo. = My gift for you. Nasa akin ang pera. = The money is with me. Moreover, oblique pronouns can be used as a genitive pronoun when SUCCEEDED by the word they modify, "sa" is omitted: Iyong ballpen = Your ballpen Aking bahay = My house *Kong and iyong are ko and iyo with the linker "-ng". When you see kong and iyong, you can be sure that they were used as genitives because of the presence "-ng" which is essential to link them to the words they modify. For more info about linkers, see: http://tagalog1.com/Lesson_View.asp?Lesson_ID=44 Note that Indirect pronouns can ALSO act as genitive pronoun when PRECEDED by the word they modify: Green ang pangalan ko. = Green is my name. --> the focus shifts on "Green" which happens to be my name. Other examples: Ballpen mo = Your ballpen Bahay ko = My house Phew! I hope I made it clear. ;)

@sharlalaw Another easier way to distinguish the use of indirect from direct pronouns is this: Let's use the rootword "kagat" = bite "nakagat" = bit unintentionally Nakagat ako = I was bitten Nakagat ko = I bit "kinagat" = bit intentionally Kinagat ikaw/ka = You were bitten Kinagat mo = You bit :)