##  [Tightness](/tightness) 

  ##  [Tightness](https://puremath.quantumdictionary.io/tightness-0) 

  

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- Mathematics & Logic -

**Pure Mathematics Dictionary**

 







 

 

 

 



 

 

 

 

Definition

The least cardinal κ such that for every subset A of a space and every point x in the closure of A there exists a subset B⊆A with |B|≤κ and x in the closure of B; this invariant measures how closures are controlled by small subsets and is denoted t(X) or T(X).