well lets say you have 10 rows, and the person inserts 40 words. Are you going to set some kind of limit? If not, then will you only insert the first ten words?
Anyways, to put each word into a different array key, i'd use explode(). keep in mind that words are differenciated by a space. So you'd explode by a space to seperate each word into a different key in your array. Then, loop through the array and insert into your database.
Cgraz