It refers to the partial payment made on a claim. It is a Latin word which means only to a certain extent. The term is applied for making a claim.
The word can be used in a sentence to indicate a kind of reason, like “I have a pro tanto reason to tell you about different types of investment products or know-how to invest in businesses or find out about buying asset class types.”
Sometimes, it is used to show an obligation that can be ruled out in certain other situations. It can be used to describe incomplete funds given by the party for getting ownership of an asset.