Let’s take a look at how we read
and write integers. Numbers like eight, negative four,
15, negative 76, and zero are all examples of integers. An integer is any number in this
set, where the dot dot dots on either side means continues without end. The word “integer” comes from the
Latin word that means “whole.”
Another way to say that is that an
integer is a number that can be written without any fractional parts. Numbers like one-half, one and
six-tenths, negative five and four-tenths are not integers; they cannot be written
without fractional parts. Here’s a number line with some
integers marked on it. Positive integers are integers that
are greater than zero. Negative integers are integers that
are less than zero. Zero is neither positive nor
negative. Let’s look at some examples of how
we use positive and negative integers.
Parts of New Orleans,
Louisiana, sit below sea level by nearly seven feet. Write the elevation value as an
So here’s what we know. We know seven feet and we know
below sea level. We know we’re dealing with
seven, but should it be a positive seven or a negative seven? If you guess negative seven,
you’re right. Since we’re dealing with an
area that’s below sea level, negative seven is how we represent the elevation of
those parts of New Orleans.
Speaking of sea level, if a
place is exactly at sea level, what integer would represent that? The answer is zero. Anything that’s neither above
sea level nor below sea level sits exactly at sea level and would be at an
elevation of zero.
Next up a true or false
question, true or false: negative 63 is an integer.
What do you think? It’s true! Negative 63 has no fractional
parts or components; so it is by definition an integer.
Is seven and two-tenths an
integer? Any thoughts? Seven and two-tenths is not an
integer. Another way to write seven and
two-tenths would be to have a seven with a fraction of two over ten. This fractional piece means
we’re not dealing with an integer here. Decimal numbers, because they
have fractional pieces, are not integers.
Let’s quickly summarise the words
we’ve been using. An integer is a number written
without fractional parts. A positive integer is an integer
that is greater than zero. And finally, a negative integer is
an integer less than zero.