A more thorough explanation:

MATERTERA MAGNA

MATERTERA MAGNA is a Latin term used in Roman law to refer to a great-aunt, who is the sister of one's grandmother.

An example of MATERTERA MAGNA would be the sister of your grandmother on your mother's side. For instance, if your mother's mother had a sister, she would be your great-aunt or MATERTERA MAGNA.

Another example would be if your father's mother had a sister, she would also be your MATERTERA MAGNA.

The examples illustrate that MATERTERA MAGNA refers to the sister of one's grandmother, whether it is on the mother's or father's side. It is a term used in Roman law to describe the relationship between family members.