The words “τάχατες” and “τάχα” come from the same root and they are synonyms. When they are used in a sentence they express question, doubt and uncertainty. “τάχατες” is more informal than “τάχα”.
Τι τάχατες ζητάει;
Τι τάχα ζητάει;
Τι ζητάει;
All these phrases mean the same thing :“What is he asking for?”
The first two of them show much more doubt and uncertainty than the third.
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.