Don't be confused by the subscripts.

别被下标弄迷糊了。

麻省理工公开课 - 热力学与动力学课程节选

While we're here, our third notation for strategy, I'm going to use little "s" without an "i," no subscripts: little "s" without an "i," to mean a particular play of the game.

说到这,我们来定义第三个标记符,我们用不带下标的小写s,来表示某一次博弈

耶鲁公开课 - 博弈论课程节选