I have read in many places on the Internet that "yeah" is considered unprofessional. And that using "yes" is preferred and considered more formal. What is the reason behind it?
Because it is informal and colloquial.
yeah adv. Informal Yes.
yeah American English, colloquial, by 1863, from drawling pronunciation of yes.
You can check this similar question as well:
Because "yeah" is an informal and almost lazy way of saying yes. In yeah,you are not pronouncing the word yes correctly.
protected by MetaEd♦ Jun 22 '18 at 20:58
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