` ` ` ` ` `In a mathematical document,
it is necessary to follow mathematical conventions
not just in display equations,
but also in the body of the text,
for example by making variable names like italic.` `
Although this could be done by surrounding the appropriate parts
with
.EQ
and
.EN,
the continual repetition of
.EQ
and
.EN
is a nuisance.` `
Furthermore, with `-ms',
.EQ
and
.EN
imply a displayed equation.` `

` ` ` ` ` `EQN
provides a shorthand for short in-line expressions.` `
You can define two characters to mark the left and right ends
of an in-line equation, and then type expressions right in the middle of text
lines.` `
To set both the left and right characters to dollar signs, for example,
add to the beginning of your document the three lines
.EQ

delim %%

.EN

Having done this, you can then say things like
Let %alpha sub i% be the primary variable,
and let %beta% be zero.` `
Then we can show that %x sub 1% is %>=0%.` `
This works as
you might expect _
spaces, newlines, and so on are significant
in the text, but not in the equation part itself.` `
Multiple equations can occur in a single input line.` `

` ` ` ` ` `Enough room is left before and after a line that contains
in-line expressions
that something like
does not interfere with the lines surrounding it.` `

` ` ` ` ` `To turn off the delimiters,
.EQ

delim off

.EN

Warning: don't use braces, tildes, circumflexes, or double quotes as delimiters _
chaos will result.` `