The Baire classes of continuous real-valued functions on a topological space $X$ are defined as follows:
- continuous functions are Baire-0;
- functions that are the pointwise limit of a sequence of continuous functions are Baire-1;
- for all $\alpha \in \mathbb N$, functions that are the pointwise limit of a sequence functions of Baire class less than $\alpha$ are Baire-$\alpha$.
Wikidata ID: Q2976036