Oppa (오빠) is a Korean term used by women to refer to an older male who is close to them in age, usually no more than 10 years older. It literally translates to "older brother" and is used in close relationships. Oppa is a term of endearment and is often used in romantic relationships. However, it can also be used to refer to an older male friend, even if he is not related by blood. Oppa is a hierarchical term that shows the social status of the subject and is used to show respect. It is important to note that only women can use the term oppa.