STI

noun

ˌes-ˌtē-ˈī 

plural STIs

: any of various diseases or infections (such as gonorrhea, genital herpes, chlamydia, hepatitis B, or HIV) that are typically transmitted by direct sexual contact but may sometimes be spread by nonsexual means (such as childbirth or sharing needles)

called also STD

Examples of STI in a Sentence

Recent Examples on the Web

The funding would reimburse services provided to Oakland County residents, including cancer screenings, annual wellness exams, STI testing and treatment, contraception, and reproductive health counseling. — Alysia Burgio, CBS News, 13 Aug. 2026

Sometimes, the differences are fairly obvious; the wing on an STI versus a normal Subaru WRX comes to mind. — Caleb Jacobs, The Drive, 22 July 2026

Rainbow Community Center presents an afternoon of pride, visibility, celebration and resilience with live performances, DJs, community vendors and resources, a kids’ area, food and free HIV/STI testing. — Kate Bradshaw, Mercury News, 30 May 2026

Research has linked it not just to vaginal symptoms, but also to fertility, pregnancy outcomes, STI risk, gynecologic cancers and more. — Helen Carefoot, Flow Space, 28 May 2026

Word History

Etymology

sexually transmitted infection

First Known Use

1983, in the meaning defined above

Medical Definition

STI

abbreviation or noun

ˌes-(ˌ)tē-ˈī 

: any of various diseases or infections (such as gonorrhea, genital herpes, chlamydia, hepatitis B, or HIV) that are typically transmitted by direct sexual contact but may sometimes be spread by nonsexual means (such as childbirth or sharing needles)

called also STD