Practice working with suffix endings ly and y. This worksheet activity asks you to cut out different list of words, sort them into either an ly or y Grammar worksheet, Suffixes worksheet, Math Reading Science Tests for Grades 5 , Practice Sample Test, Free Online Worksheets. TEENs completing this third grade reading and writing worksheet practice using suffixes by adding -ful or -less to words to finish sentences. –noun 1. Grammar . an affix that follows the element to which it is added, as -ly in kindly. 2. something added to the end of something else. –verb (used with.