ANSWER:

Yes it is awrah as it is not part of your chin, it is part of the neck. 

My question is Is underneath part of the chin part of awrah. Can I show my underneath part of the chin when wearing hijab When I am wearing hijab wheather if I am praying or just outside in front of non mehrams my hijab slips and people can see my underneath part of the chin. It doesn’t matter how tightly I wear hijab it still happens.

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