Multiple sex partners (MSP) is the measure and incidence of engaging in sexual activities with two or more people within a specific time period. Sexual activity with MSP can happen simultaneously or serially. MSP includes sexual activity between people of a different gender or the same gender.
The term polyamorous is a behavior and not a measure describing multiple sexual relationships at the same time.[1]
Young people having MSP in the last year is an indicator used by the Centers for Disease Control and Prevention (CDC) in evaluating risky sexual behavior in adolescents and a tool in the monitoring of changes in HIV/AIDS infection rates and deaths worldwide.[2]