# Poincaré conjecture

Definition from Wiktionary, the free dictionary

## English[edit]

### Noun[edit]

**the Poincaré conjecture** (singular only)

- That the only simply connected, closed 3-dimensional manifold is a sphere.

#### Usage notes[edit]

- This is still (2008) known as the
*Poincaré conjecture*but is now a theorem rather than a conjecture.