My thoughts -- in English, we often skip the helping word that goes after a verb like this. For example, "I say we should go" and "I believe you're wrong" have an implied "I say THAT we should go" and "I believe THAT you're wrong." In Spanish, you always say it. It has to be "creo QUE" and "digo QUE".
I'm still figuring it out too, but that seems to be the case so far!
When you think about it, the real question is why can't you use the conjunction in English?
In general, in English sentences of the form "He says thus-and-such," it's okay (and arguably clearer) to introduce the subordinate clause (i.e., the thing he says) with the conjunction "that." The fact that you can't do this in English when the subordinate clause is "yes" or "no" is a strange exception.
The whole thing makes a lot more sense when you realize this.
It's not just yes or no. "He says hello", "He says nothing", "He says bite me", "He says just leave now". In all these cases you'd need to do some more work to make it into a subordinate clause, because what's really happening is that you are quoting somebody directly, and neglecting the formality of quotation marks. English doesn't let you toss a direct quotation into a subordinate clause grammatically.
Bob: "You should go".
Me, reporting back:
"Bob says, 'you should go'" - OK
"Bob says that WE should go." - OK
"Bob says that you should go." - probably not what Bob meant; sounds like I am trying to duck out of it. :)
Bob: "Bite me!"
Me reporting back to the team:
Bob says bite me. - OK. Ambiguity can be exploited for humor.
Bob says that bite me. - Not acceptable.
Bob says that you should bite me. - Structurally correct but conveys wrong meaning,
Bob says that you should bite him. - OK
I'm still learning how Spanish handles all these cases.
There is one thing English speakers sometimes do that clarifies who is saying what, although it's grammatically incorrect. Actually say, "quote" or "and I quote" before the quote. Frequently while making quote marks in the air with the index and middle fingers of both hands near the head.
"Bob says (and I quote), 'Bite me!'"
In spanish, not everything directly translates over to English. While we say "I say yes" the same phrase means "Digo que sí". The que in this sense is required but does not come with a translation. In Spain we also say things like "Que sí" and "Que no" for things like No way and For sure. You can also use que with an adjective to make it an exclamation of the word i.e. "Que mono" which means how cute! So in other words, Que is not always directly translatable.
I know, but that's not nearly as much fun. I once puzzled a very nice French man by asking him why his people called each other cabbages. We sorted it out eventually. I speak only a few words of French, but I found people to be very friendly when, depending on their age, I "merci beaucoup, madame"-d them, or "merci beaucoup mon petit chou"-d them with a practiced accent. It is the little things, isn't it?
Also... French pastry. How I miss it!
"que" is used in a lot of expressions.
digo que si = yes
digo que no = no
creo que si = i think (believe) so
creo que no = i don't think (believe) so
que bueno! = good!
qué malo! = bad!
qué padre! = awesome!/fantastic!, etc
qué tal = how are you
qué bonito! = how pretty!
qué lástima! = what a shame!
qué bien! = great!/well done!/excellent! etc
qué onda? = what's up?/what's happening?
there are many more and some vary in usage by country
Once again I believe this really has no explanation....this is just my opinion. It is just one of those phrase that you have to know. Duo is great to get a solid base. When you watch Spanish tv you start focusing less on actually translation but more on that meaning of something.
You can think of it as 'Yo digo'/'I say' as the dialog tag of who is speaking and the 'que' acts as the conjunction (comma) and sets up quotes, "sí"/"yes". 'I say yes' = 'I say,"yes"'. So if you see the pattern of describing who is speaking/spoke then a "que" and followed by what looks like a quote then you ignore and drop the "que" when you translate.
The "que" here is a conjunction used to introduce a subordinate clause. It serves the same function as the conjunction "that" in the English "I say that it is so."
The fact that you cannot use the conjunction in English when the subordinate clause is "yes" or "no" (even though you can do so with any other subordinate clause) is an odd exception in English grammar that you have to unlearn in this case.
What is the connection between :"dijo", and "digo". It looks almost the same. Does it have the same meaning? (mi hermana me dijo que no", and this one ? ...and in the same lesson there was also "dicen" "los ninos dicen que ...". I am getting a little bit confused here. Is it the same word?
They are both conjugated forms of "decir" http://www.spanishdict.com/translate/decir#conjugation "digo" = "I say" and "digo" = "he/she/you(formal) said(past tense)"
My interpretation of this is something like : "I say yes to that".
As "que" can be a non specific definitive noun. 'That'.
And if you consider in English when the phrase "I say yes" is said, it is usually in response to a specific thing.
So that is what the 'que' is in that sentence, it is the specific thing that someone it saying yes to.
Is it correct ? I don't know.
If you're on a US or UK Mac, type 'Option'+'e' to get the acute accent, then 'i' to put the accent on the 'i'.
Otherwise, each Duolingo page where you're expected to type Spanish has an array of buttons for the non-English Spanish letters, beneath the text-entry field.