
In the past few minutes we've touched on a
lot of concepts that are going to play a

really central role in the rest of the
course and really in all math going

forwards from here. So I would like to do
a review of the algebra vocabulary that

we've covered so far. I think it's
actually going to amaze you how much we've

already gone over in a pretty short amount
of time. So first thing first, we have

numbers, as one might expect in math. So
what are some examples of numbers? Well,

we could have any number of things. So
like we learned in the very beginning of

this course, they're all different kinds
of numbers. Some that are pretty simple

and we use all the time, like 0 or 1 or
46, and some that are a little bit more

special, like the root of 2 or pi. Then in
contrast to numbers, we also learned about

variables. So, here we have all different
kinds of symbols, we have some letters, we

have some sillier things like hearts and
smiley faces, we got some greek letters.

But regardless of what we write variables
as they all have the same purpose, as we

learned earlier. Variables are symbols
that we use in equations and expressions

that serve as slots into which we can plug
other numbers to make our expressions take

on different values. So comparing numbers
and variables, numbers have fixed values.

They inherently show certain quantities.
Variables, however, don't show outright

what they stand for, they're just place
holders into which we can insert different

numbers. One thing to take note of when
we're looking at what's inside each of

these circles is that we actually have a
symbol on the number side. That's this pi

right here. Since pi is an irrational
number, it extends for an infinite number

of decimal points. Now, it took me an
awfully long time to write all of this

out. So if I were to write even more, that
would take me even longer. To make our

lives much more simple, we give this
infinitely long number a special name,

which is pi. A similar thing happens when
we write square roots. We have a number,

2, right here but we also have a square
root sign over it. Since the root of 2 is

also an irrational number the square root
sign is just another way of taking a

shortcut to not have to write out an
infinite number of decimals. So bottom

line, when you see symbols, they're almost
always variables. They'll be certain

cases. Which you'll become well acquainted
with when you see things like pi or like a

square root sign that are symbols of some
sort but represent numbers.