Question 165371
We know that there are 26 letters in the Alphabet and 7 distinct letters (letters cannot be duplicated)
so the first letter can be any of the 26
the second letter can be any of the letters except for the first letter or (26-1)
the 3rd letter can be any of the 26 letters except for the first two letters or 26-2=24 possibilities
...
so each letter loses one more possibility
1st*2nd*3rd*4th*5th*6th*7th=total possible seven-letter words 
{{{26*25*24*23*22*21*20=3315312000}}} possible seven-letter words