A Course in Finite Group Representation Theory
《A Course in Finite Group Representation Theory》 · 第 288 页 · Section 7.1「Transcendence Bases」
The result we have just proved allows us to define for an arbitrary field extension $L/K$ its transcendence degree $\operatorname{transdeg}_K L$ as the cardinality of a transcendence basis of $L/K$.