How many two letter words can be formed from 26 English letters? There are 26 English letters(a-z).
From layman approach, How can one calculate the possible two letter words from these 26 English letters?
 A: There are 26 choices for the first letter. For every choice of first letter there are 26 choices for the second letter. Thus there are 26 times 26 of them in total, or 676.
A: I'm assuming we're not talking about which ones are actual words.
There are 26 possibilities for the first letter and 26 for the second. Multiply them and you get 676 total possible "words" (but this includes things like ZQ and XT.)
If you want actual words, this site says there are 96 in the OSPD4, the Scrabble dictionary.
And if you want a better estimate, there are 6 vowels and 20 consonants (counting Y as a vowel). They can go in either order (so we can have words like OF). 6 times 20 times 2 is 240 possible words.
A: $$
\begin{array}{c|c|c|c|c|c|c|c}
\text{alphabetical order: } & aa & ba & ca & da & ea & fa & \cdots \\
& ab & bb & cb & db & eb & fb & \cdots \\
& ac & bc & cc & dc & ec & fc & \cdots \\
& ad & bd & cd & dd & ed & fd & \cdots \\
& ae & be & ce & de & ee & fe & \cdots \\
& af & bf & cf & df & ef & ff & \cdots \\
& ag & bg & cg & dg & eg & fg & \cdots \\
& \vdots & \vdots & \vdots & \vdots & \vdots & \vdots &  
\end{array}
$$
26 columns; 26 in each column.
A: More generally the formula is:
$x^y$
where $x$ is the number of items in the set (26 possible letters in this case), and $y$ is the number of occurrences of that set of items (series of 2 letters in this case).
So,
1 letter (A) = $26^1 = 26$
2 letters (AA) = $26^2 = 26*26 = 676$
3 letters (AAA) = $26^3 = 26 * 26 * 26 = 17,576$
4 letters (AAAA) = $26^4 = 26 * 26 * 26 * 26 = 456,976$
etc.
