Another one that can't translate familial relationships: an adoptive mother is NOT a stepmother. The only way you get a stepmother is if your father marries a woman who is not your legal (by birth or adoption) mother. An adoptive sister is just your sister, not your foster sister, not your stepsister.
Biological mother = birth mother
Adoptive mother = Legal mother
Stepmother = mother by marriage, woman married to your father(or, alternatively, woman married to your mother)
Foster mother = legally appointed guardian mother, usually due to being orphaned or separated from parents
You can have only one birth mother, barring being an alien or some weird science fantasy or magic scenario. You are likely to have only one adoptive mother. You can have more than one stepmother, though if your father/mother remarries again, your stepmom becomes your ex-stepmom. You can have multiple foster moms, though they become former foster moms after you leave them(though you may still think of them as "one of my foster moms")
A
mother-in-law is the mother of your spouse. A
godmother is a close family friend given a ceremonial/honorary role by your parents. A
mother superior and a
reverend mother are leaders of clerical orders(i.e., nuns).
Someone please translate this into Russian! lol