IV - Definition and Overview

IV may refer to:

• In medicine, an acronym for intravenous, as in "IV drip" (or simply "IV") for intravenous drip, or "IV drug use" for intravenous drug use; see also intravenous therapy
• In cryptography, an acronym for initialization vector
• InterVarsity Christian Fellowship, a Christian ministry for college students
• the Roman numeral for 4
• In music,
  • the roman numeral IV is the subdominant scale degree, chord, or diatonic function, when distinguished IV = major and iv = minor.