Disso is a combination of " de + isso ". To talk about a subject: I am talking about this = Eu estou falando de isso = Eu estou falando disso. I'm sure about this = Eu estou certo de isso = Eu estou certo disso But we do not use " de isso ", it's always turned into " disso ". Same goes with " desse " = de esse I got the file from this computer = Eu consegui o arquivo desse computador Deste = De + este Desta = De + esta ____ Disso is used when you have no specific noun, it's mostly used in sentences like this: Eu sei disso = I know about this Eu falei disso com você ontem = I talked to you yesterday about this Disso eu não posso ter certeza = About this I cannot be sure. Olha o inseto, você tem medo disso? = Look to the insect, are you afraid of this ___ Isso is used whenever you don't have to put the preposition DE before the word: Isso eu sei! This I know Isso eu te falei! I told you this Eu peguei isso para mim! I got this for me Notice that if I wrote in English using " about " it'd have to be " disso "

You can use "ISSO" instead of "ISTO" in informal conversations, like: Isso é bonito (This is beautiful) Isso é caro! (This is expensive!) Usually at the begining of a phase. "DISSO" is used after the verb (usually). Eu gosto disso. (I like this)

In portuguese there is abreviaciones (abreviations) for to be more FLOW flowed, so its better or more speed(speeder) to say disso than de isso., like in some wors in english ¨¨The Only exception¨¨ the pronunciation is De onli eks-ssepshoen but is reduced at D´onli excepshoen between its 2 first words okey Good luck