Really don't know about that, i only call my mother is mom
Mom
In the English language, you can refer to you mother as "mother" or in informal situations as "Mom" or "Ma." Some people, especially as adults, are on a first name basis with their parents and call them by their names.
Two mother-in-laws call each other "daughter-in-law."
Whatever names they were given at birth.....
A mother.
Tired.
If she is your birth mother, she is your mother by necessity of implied Definitions, and physics. Some folks, who were adopted at birth, regard the adoptee's as the true parents, but the Fact is, you can only have one Birth mother, so you could refer to her as, "My Birth Mother" this does not prevent you from calling your adoptee Mother, Mother as well. The Traditional Roles of Females Via History, would more then suggest that "Mother" is not necessarly the Birth Mother, but rather the Care Provider of any and all, as in Motherhood.,,Mother Earth, Mother Teresa, Mother Nature, Etc.
Kharybdis
A pore.
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Quadrilateral
If you don't want to call your step-mother 'mom' or 'mother' then ask her permission to call her by her first name.