Column addition is a mathematical operation in which two or more numbers are added together to find the sum. It is a basic arithmetic skill that is taught in elementary school and is used in everyday life. In this crossword, the solutions for the term 'column addition' are IST (3 letters), ONES (4 letters), and IONIC (5 letters). IST stands for 'In Same Total', which is a method of column addition where the numbers in each column are added together and the total is written at the bottom of the column. ONES stands for 'ONES Place', which is the rightmost column in a column addition problem. IONIC stands for 'Ionic Columns', which is a method of column addition where the numbers in each column are added together and the total is written to the right of the column.