How to get the equation to look in a required format?

Question

I am still new in LaTeX - beginner. How can I have the equation to look like this (the example is shown in ms word):

Lexical level:      f o x + plural (‘+’ is a morpheme boundary)

Surface level:      f o x e s

Two-level rule:     e:+ ↔ x:x _ 0:s

The 'f' at lexical level must be align with the 'f' at the surface level. Do I have to put it in a table so that each of the characters can be aligned?

Answer 1

An alternative would be a tabbing environment:

 \begin{tabbing}
 Lexical level:\qquad \=f~\=o~\=x + plural (`+' is a morpheme boundary)\\
 Surface level:       \>f \>o \>x~e~s\\
 \\
 Two-level rule:     \>e:\textsuperscript{+} $\leftrightarrow$ x:x \_ 0:s
 \end{tabbing}

\= sets a tab stop on the first line. \> moves to it on the next line and subsequent ones.

Answer 2

If you want to align the 'f' on each level, a table is probably easiest:

\begin{tabular}{rl}
Lexical level:    &    f o x + plural   \\
Surface level:    &    f o x e s        \\
\end{tabular}

The basic table environment is tabular. The rl means the table has two columns, the first right-justified and the second left-justified. Then just put in your entries row-by-row, using & to skip to the next column and \\ to skip to the next row. This is probably enough for your current purposes, but when you end up wanting to make a proper table you should check out the LaTeX Wikibook.

As for the other part of your question, I'm afraid I don't have enough linguistics training to know what "e:+ ↔ x:x _ 0:s" should look like. It would be great if you could point us to an example of what you'd like to get. That being said, you can get ↔ with $\leftrightarrow$; an underscore with \_ or a longer underlined space with \rule{1cm} or \underline{\hspace{1cm}}; and ∅ (if you're looking for that instead of 0) with \emptyset or \varnothing.