How do I included mathematical symbols into my body text. In this example I want to include the Greek lowercase letter alpha (α):

The ball is deflected by an angle \alpha away from the line of approach of the cue

When I compile the above I get the following error:

! Missing $ inserted.
<inserted text> 
                $
l.101 ...e cue

Mathematical symbols must be declared in a mathematical environment. In the body text this can be invoked by surrounding the symbol in dollar symbols, i.e.:

The ball is deflected by an angle $\alpha$ away from the line of approach of the cue

If the text in some of your chapters appears to be too small it's possible that there is an unclosed acknowledgement in an earlier chapter that is bleeding through to the rest of the document, e.g.,

\acknowledgement{
Here is some acknowledgement text
}

Instead, your acknowledgement should be encased in begin/end, as follows:

\begin{acknowledgement}
Here is some acknowledgement text
\end{acknowledgement}

The following text (including that in later chapters) should now be typeset appropriately. The problem (for me) was caused because everything in the document from this point onwards was being typeset as acknowledgement text.