Social identity is a person's sense of self derived from group memberships. It answers the question: Who am I in relation to others? I am a teacher, a mother, a Nigerian, a Muslim, a Democrat. These identities shape how we see ourselves and how others see us.

Henri Tajfel developed social identity theory in the 1970s. He showed that people favor their own groups even when group membership is arbitrary. Social identity provides self-esteem, belonging, and meaning. It can also fuel prejudice when groups compete.

Sources of social identity

• Family and kinship
• Occupation and education
• Race, ethnicity, and nationality
• Religion and ideology
• Gender and sexuality

Identities can conflict. A woman may feel torn between her identity as a mother and her identity as a professional. Identities can also change. A person may embrace a new identity after migration, conversion, or recovery. Social identity is not fixed. It is negotiated and performed.