Consider the sequence 10.20, 11.40, 12.10, 13.40 where each term
represents the amount of money you earned as interest on your savings
account for each of four years.
The sum of the
terms, 10.2 + 11.4 + 12.1 + 13.4, represents the total interest
you earned in the four year period. Such a sequence
summation is called a series
and is designated by S_{n} where n represents the
number of terms of the sequence being added.
S_{n}
is often called an n^{th}
partial sum, since it can represent
the sum of a certain "part" of a sequence.

A series can be represented in
a compact form,
called summation notation, or
sigma notation.
The Greek capital letter sigma,
,
is used to indicate a sum. 
"The summation from 1
to 4 of 3n":




Check out how to use your
TI83+/84+ graphing calculator with
summation notation.
Click here. 

