I know it originates from head shrinking, but it doesn't help me a lot to understand the etymology.Why are psychiatrists called that?Is it like my head is swollen [from anguish, misery, stressThus we say:You never know, which is why but you never know.That is why and goes on to explain:There is a subtle but important difference between the use of that and which in a sentence, …
The Power of ‘Why’ in Safety - EHS Daily Advisor
The Power of ‘Why’ in Safety - EHS Daily Advisor

The Power of ‘Why’ in Safety - EHS Daily Advisor of Why Is Joy Reid Leaving MSNBC? This Is Why You Should Be Worried! .

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Good explanation of why it's optional in this case, although i'm not convinced that reason is the only reasonable antecedent of why.For example, the explanation why is a common usage, and i don't …I don't know why, but it seems to me that bob would sound a bit strange if he said, why is it that you have to get going? in that situation.