Average
The word average is often used in two different ways.
Either as a general noun to include
ideas such as mode, median or mean.
But sometimes the
word 'average' is used instead of the word 'mean'.
MODE
the one that occurs most often
MEDIAN
the middle one when numbers are placed in order of size
MEAN
add all the numbers together to get a total
and then
divide by the number of numbers to get the mean.
Sum
The technical meaning
of the word sum in mathematics is the answer that you
get when you add numbers together.
Sometimes people become
confused when the word sum is used in the sense of
'do this sum'
when what we are actually saying is
'do this calculation'.
It can be even more
confusing if
the 'sum' referred to is a subraction, multiplication
or a division.
It may be less confusing
to restrict the word 'sum' to the result of addition
and use the word calculation elsewhere.
Whole Number
The term 'whole number'
is used very often to mean the numbers
0, 1, 2, 3, ....
But the term is also
used to mean the same as the word 'integer'
which are the whole negative numbers as well as the
whole positive numbers
..., -3, -2, -1, 0, 1, 2, 3, ...
Fortunately,
there is generally little to worry about because the
meaning is usually quite clear in the context in which
it is used.