The precise name of a symbol in mathematics sometimes depends on what you're using it for. For example, × is often referred to simply as the multiplication sign, but if you need to distinguish scalar from vector multiplication, you might refer to it more specifically as the cross multiplication sign, vector multiplication sign, or something similar.
In your second example, the ・ symbol is called dot. The product of two numbers multiplied using the dot operator is the dot product. In some contexts, you might call it the scalar multiplication sign.
Outside of programming, we usually only use * for multiplication when we can't type ×. The * symbol is usually called the asterisk or star, though if you're using it as a multiplication sign, you might call it that, instead.
The last example appears to be using a period. Like *, I assume this is simply because they couldn't type ・. I could call this a period, but more usefully, I could call it whatever it represented: in this case, I might call it dot, since it's standing in for ・.
I'm guessing that you are referring to McCawley's numbering system for example sentences:
(1) a.
a′.
a″.
a‴.
b.
... and so forth.
These are not actually English words but typographic symbols. Like the tree diagrams, they're not really intended to be spoken.
If you have to speak them, you may as J.R. suggests say a-prime, a-double-prime, etc. (which is a use borrowed from mathematics), or you may as FumbleFingers suggests say a-tick, etc. (but that is a British rather than US usage).
Best Answer
It is an upper case Sigma, from the Greek alphabet.
It is almost always used to denote a summation:
and is therefore (technically) called a summation symbol, as others pointed out in the comments.