Π1

π1 or Π1 or Pi1, may refer to:

• π₁, a notation for the scalar projection onto the first component
• π₁, the fundamental group of a topological space
• Π₁, the fundamental groupoid of a topological space
• Π⁰₁, or Π₁, a classification in the arithmetical hierarchy

• Yudo π1 (Pi1), a car model
• Pi1 (gene), a gene found in Oryza sativa for fungus resistance
• Pi1, a type of torpedo warhead used by Germany in World War II; see List of World War II torpedoes of Germany

• Pil (disambiguation)
• PII (disambiguation)
• P1 (disambiguation) (Greek: π1; romanized "p1"; pronounced "pi1")
• Pi (disambiguation)
• π (disambiguation)
• All pages with titles containing Pi-1
• All pages with titles containing Pi1
• All pages with titles containing π1