The term 'SO THAT'S IT!' can be broken down into four crossword solutions: AHA (3 letters), OHO (3 letters), ISEE (4 letters), and OHISEE (6 letters). AHA is an expression of surprise or realization, often used to express understanding or agreement. OHO is an exclamation of surprise or realization, similar to AHA. ISEE is an acronym for 'I See, ' which is a phrase used to indicate understanding. OHISEE is an acronym for 'Oh, I See, ' which is a phrase used to indicate understanding or agreement. All four of these terms are used to express understanding or agreement, often in response to something that has been said or done.