There are two types of basic trees in TAG: initial trees (often represented as ' α {\displaystyle \alpha } ') and auxiliary trees (' β {\displaystyle \beta } ').
在 TAG 中有两个种类的基本树：“初始”树（经常被表示为 ' α {\displaystyle \alpha } '）和“辅助”树（' β {\displaystyle \beta } '）。