MyVocabulary.com offers 14 PREFIX puzzles with the grade level of each word marked to the right of the word beginning with a prefix. Use eight grade level words for each prefix."IN-IM" prefix words: Indefinite - 7, Injustice - 6, Immortality - 8, Impatience - 7, Impractical - 7, Improbable - 8, Insatiable - 7, Invalid - 7