The great aunt in your family tree is the sister of one of your grandparents.
Your great aunt is either your father or your mother's aunt.
The great aunt is the great niece's baby's great-great aunt.
The opposite gender of a great uncle is a great aunt. A great uncle is the brother of one of your grandparents, while a great aunt is the sister of one of your grandparents. Both terms refer to relatives in the same generational level within a family tree.
Your aunt's great grandson is your first cousin twice removed.
second cousin
Well, isn't that a happy little family tree question! Your aunt's husband's sister is your aunt by marriage. Just think of all the lovely family gatherings and painting sessions you can have together!
Since your mother and her sister have thesame aunts and uncles, your mother's sister's aunt is your grand aunt or, as some sat, your great aunt.
In Yiddish, "great aunt" is referred to as "זיידע" (zayde), which can also mean "great aunt" or "aunt by marriage." Another term specifically for a great aunt is "שוועסטער-פֿרײַנד" (shvester-freind), which translates to "sister's friend." The usage may vary depending on regional dialects and family traditions.
The same place as if you were married.
Your great-aunt
If you are truly a great aunt then no, grand aunt is fine, but if the family persists on calling you 'great aunt' then go with the flow. Both great aunt and grand aunt mean the same thing, the sister of one's grandparent. Some communities prefer one and some prefer the other.
Your aunt may be the sister of your father or mother, or your uncle's wife. In the former case, an aunt's sister could be another aunt, or could be your mother. In the second case, the sister of your uncle's wife has no direct relationship to you at all.