π1 or Π1 or Pi1, may refer to:

Mathematics

* π₁, a notation for the

scalar projection In mathematics, the scalar projection of a vector \mathbf on (or onto) a vector \mathbf, also known as the scalar resolute of \mathbf in the direction of \mathbf, is given by: :s = \left\, \mathbf\right\, \cos\theta = \mathbf\cdot\mathbf, wh ...

onto the first component * π₁, the

fundamental group In the mathematics, mathematical field of algebraic topology, the fundamental group of a topological space is the group (mathematics), group of the equivalence classes under homotopy of the Loop (topology), loops contained in the space. It record ...

of a topological space * Π₁, the

fundamental groupoid In algebraic topology, the fundamental groupoid is a certain topological invariant of a topological space. It can be viewed as an extension of the more widely-known fundamental group; as such, it captures information about the homotopy type of a to ...

of a topological space * Π⁰₁, or Π₁, a classification in the

arithmetical hierarchy In mathematical logic, the arithmetical hierarchy, arithmetic hierarchy or Kleene–Mostowski hierarchy (after mathematicians Stephen Cole Kleene and Andrzej Mostowski) classifies certain sets based on the complexity of formulas that define th ...

Other uses

Yudo π1 The Yudo π1 or Yudo Pi1 is a Subcompact car, subcompact crossover SUV produced by the Chinese New energy vehicle, NEV manufacturer Yudo Auto. The side profile heavily resembles a second generation Haval H1 due to the platform being shared by Hav ...

(''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 List of World War II ''Kriegsmarine'' torpedoes ''Kriegsmarine'' torpedo designation system The first letter indicates the diameter: * G = 53 cm (21 in) * F = 45 cm (17.7 in) * H = 60 cm (23.7 in) * M = 75 cm ( ...

Mathematics

Other uses

See also