'I talk slow' should be accepted. Reported. 'Slow' and 'fast' are flat adverbs, meaning they don't have the 'ly' ending. Check it here: http://www.learnersdictionary.com/qa/Slow-Slowly-and-Flat-Adverbs
Also - speaking a language- is not an exact science.
Dictionaries and grammar references, They try to explain rules
However those rules can not be interpreted for every sentence.
One set of rules and definitions for one particular word, can not be used in the same way for every sentence construction - in either the source or the target language.
So - one can not refer to ... well any secondary reference - be it the one you refer to - or to other more mainstream ones, such as the Oxford, or Collins dictionaries.
For dictionaries, and also grammar references - are attempts to classify and codify a language. Yes - they are essential references for this purpose. However - in real life - they are trying to describe a language. It is not that they are the rule makers.
They are trying to describe the patterns.
Which is also why a competent translator - between source and target languages - a real human skilled in both languages ( including their cultures - perhaps especially knowing both cultures )- is ever so important.
Hello there Raftus :-D
I am an Australian.
And we would not say "I talk slow." It would just not be a sentence grouping we would use.
We would say things like :
I talk slowly
Please talk more slowly
OK, I will talk more slowly
Could/Can/Would you say this slowly for me
Could/Can/Would you speak more slowly for me
This is partially I think because to imply someone is speaking "slow" is a "offense" or a "slight" to that person.
Such are the joys of language - that they are not (mathematically) logical. That the rules of nuance - are varied and cultured.
Oh, I agree that language isn't necessarily logical. But saying it's not an exact science doesn't mean there are no rules. There exist 'flat' adverbs, and 'slow' and 'fast' are the usual examples given.
But did you read the piece I linked to? And did you notice that elsewhere in Duo, in this very Greek course, they use 'slow' as an adverb? Slow doesn't have any such 'offensive' connotation to me, also living in Australia. It just means the opposite of fast, that's all. As a matter of interest, if you want to see 'offense' in normal words, why wouldn't 'slowly' be just as 'offensive'? It just means in a slow manner.
I notice that article referred to in the original post says "but in casual speech, informal writing (such as text messages or e-mails to a friend), and even some formal writing slow is often used as an adverb.". I would agree that you do hear things like "Please talk slow", but (despite the second part of the sentence above) it isn't what I would expect to see in a formal or academic piece of work.