I've been watching some online courses and I'm having a difficulty understanding what exactly are they saying. The courses are scientific in nature and rather often an indexed symbols appear. The indexed symbols are usually written with a subscript, like this:
When refering to those, the instructor pronounced them like you would pronounce "ace of n" and "eyes of c". It seems that the suffix s is added to the letter. I have completed a non-English education, so this was new to me.
What are the rules regarding indexed symbols?
Is it simply: a's of n, or i's of c, and more importantly why?