Based on arse, new words formed by adding one letter at the beginning or end:
a - aers b - areas c - bares d - bears e - braes f - saber g - sabre h - acres i - cares j - carse k - escar l - races m - scare n - dares o - dears p - rased r - erase s - saree t - fears u - safer v - agers w - gears x - rages y - sager z - sarge
