What is used to specify an absolute reference in a formula enter a(n) before any column letters or row numbers to be kept constant when formulas are copied.?

To specify an absolute reference in a formula, you use a dollar sign ($) before the column letter and/or row number. For example, in the reference $A$1, both the column A and row 1 are fixed, meaning they won't change when the formula is copied to other cells. You can also use a dollar sign before just the column or the row to create mixed references, like $A1 or A$1.