Sometimes you see this written when you see p orbitals, one is written as plus, one is written in minus.

有时候你们看ｐ轨道时会看到，一个写成正号一个写成负号。

麻省理工公开课 - 化学原理课程节选

And this shows that G is written naturally as a function of T and p.

这表明G可以很自然的,写成T和p的函数。

麻省理工公开课 - 热力学与动力学课程节选