Definition 2

Tag 0AUZ, permanent. Cite it as [Bourbaki, Tag 0AUZ].

Lie Groups and Lie Algebras, chapter VI, § 1. Root systems

A subset $B$ of $R$ is called a basis of $R$ if there exists a chamber $C$ of $R$ such that $B = B(C)$ . If $C$ is a chamber, $B(C)$ is called the basis of $R$ defined by $C$ .

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

Definition 3, § 4
Remark 3, § 4
Proposition 4, § 2

Cites

Nothing.