The answer to whether your mom’s cousin is your uncle is not a simple yes or no. It depends on the specific relationship between your mom and her cousin, as well as on the cultural and social norms of your family.

In general, the term “uncle” is often used to refer to a brother or brother-in-law of one’s parent. However, it can also be used more broadly to refer to a close male relative who is part of one’s extended family. Similarly, the term “cousin” can refer to a range of relationships, including first cousins (who share grandparents), second cousins (who share great-grandparents), and so on.
So, if your mom’s cousin is the brother of your mom’s parent (i.e., your grandparent), then he would be your uncle. Similarly, if your mom’s cousin is married to your mom’s brother, then he would also be your uncle by marriage. In both of these cases, the relationship between your mom and her cousin is relatively close, and it would be appropriate to use the term “uncle” to refer to him.
However, if your mom’s cousin is the child of your mom’s aunt or uncle, then the relationship is more distant, and it may not be appropriate to refer to him as “uncle.” In some families, it is common to use the term “cousin” to refer to any relative who is not a sibling, parent, or grandparent, regardless of the specific degree of relationship. In such cases, it may be more appropriate to simply refer to your mom’s cousin by his first name, rather than using a familial title.
It’s worth noting that the use of familial titles can vary widely depending on cultural and social norms. In some cultures, for example, it is common to use specific titles for different degrees of relationship (e.g., “aunt” for a father’s sister, “tante” for a mother’s sister, etc.), while in others, it is more common to use a more general term like “cousin” or “uncle” for any relative beyond immediate family members.
Ultimately, the decision of whether to refer to your mom’s cousin as “uncle” is up to you and your family. If you feel comfortable using the term and it is in line with your family’s norms and customs, then there is no harm in doing so. However, if you are unsure or if it feels awkward or inappropriate, it may be best to simply use your cousin’s first name and avoid using a familial title altogether.
In summary, whether your mom’s cousin is your uncle depends on the specific relationship between your mom and her cousin. If the cousin is a sibling of your mom’s parent or married to your mom’s brother, then he would be considered your uncle. However, if the cousin is the child of your mom’s aunt or uncle, then the relationship is more distant, and it may not be appropriate to use the term “uncle.” Ultimately, the decision of whether to use familial titles is up to you and your family, and should be based on your own comfort level and family customs.