Columnar addition is a mathematical method of adding numbers vertically in columns. There are several synonyms for columnar addition, including vertical addition, place value addition, and regrouping addition. In vertical addition, the digits are aligned according to their place values, and added in columns from right to left. Place value addition emphasizes the importance of the positional value of each digit, whereas the regrouping method involves carrying over the extra digits to the next column. These synonyms are interchangeable and are commonly used in mathematics to teach children the fundamental concepts of addition and place value.