I am quite new to Tagalog, and I've been building my vocab much more than my grammar skills. I understand that na is past tense, but I just get confused when I see something for example... "Isang papel na supot na walang-laman." I do know what the sentance means, but many times in a place where I would personally put "Ng" I see "Na" instead, can someone please help me out on the use of "Na" over "Ng". What does "Na" infer on the sentence that "Ng" doesn't, and visa-versa? Answers are greatly appreciated. Thanks!