Maternal relates to a mother — maternal instinct, or the maternal side of a family. Fraternal relates to brothers — fraternal bonds, a fraternal organisation — and, in the twin sense, means non-identical. They are not a pair despite sounding like one: the counterpart of maternal is paternal.
The core difference
These are frequently treated as opposites and are not. The genuine pairs run differently.
- maternal — of a mother: maternal grandmother (your mother's mother).
- paternal — of a father: paternal grandmother (your father's mother).
- fraternal — of brothers, or non-identical twins.
- sororal — of sisters, though rarely used.
Family-tree usage
Maternal and paternal are how English distinguishes which side of the family somebody is on, because it has no separate words for the two grandmothers — unlike many languages, which do.
The twin sense
Fraternal twins means non-identical, from two eggs, regardless of the twins' sexes. Two sisters can be fraternal twins, which surprises people. The technical term dizygotic avoids the mismatch.
Frequently asked questions
What is the opposite of maternal?
Paternal, relating to a father. Fraternal relates to brothers and is not the counterpart.
What is a maternal grandmother?
Your mother's mother. Your father's mother is your paternal grandmother.
Can two sisters be fraternal twins?
Yes. Fraternal means non-identical, from separate eggs, regardless of sex, despite the word coming from the Latin for brother.