If we consider any random combination of 7 letters or characters of all existing writing systems, we will get not only all possible words with seven letter, but also get the words without meaning in any language (depends on the concept of word). So, any of the words resulting from the last group is a correct answer: Regardless of the letters that are removed from this word the meaning would not change, this meaning is, of course: NONE.

This leave us with: letters!/7!(letters-7)! - known_words, correct answers for this puzzle.

If we consider any random combination of 7 letters or characters of all existing writing systems, we will get not only all possible words with seven letters, but also get the words without meaning in any language (depends on the concept of word). So, any of the words resulting from the last group is a correct answer: Regardless of the letters that are removed from this word the meaning would not change, this meaning is, of course: NONE.

This leave us with: letters!/7!(letters-7)! - known_words, correct answers for this puzzle.