Final answer:
In the Spanish language, the verb 'ser' should be used when defining permanent relationships, such as that with a mother, since it is used for characteristics considered to be lasting or inherent.
Step-by-step explanation:
When defining a relationship or identifying someone, such as a mother, in Spanish language, the verb 'ser' should be used. This is because 'ser' is utilized for permanent or lasting attributes, and one's relationship to another person is not expected to change over time. For example, 'Ella es mi madre' translates to 'She is my mother.'
Moreover, 'ser' is used to express the nature or identity of a person or thing, professions, nationalities, religious or political affiliations, the material something is made of, possession, and the time, date, or season of an event. In contrast, 'estar' is generally used for temporary states, locations, emotions, and conditions. For instance, 'Estoy en casa' means 'I am at home,' indicating a temporary state or location.