herein herein
Herein
Herein
therein
therein
THEREIN
therein
Heroin
Herein
her, hero, in, he, I (there are only 5)
therein
therein
therein
therein
THEREIN
therein
The answer lies in the question. your required word is "seven letter", as it contains eleven letters.
If you write April 26, 2011, this contains only 5 letters, but unfortunately also contains numbers...
The word therein. They are: There I in the here her he rein ere herein and therein.