The crossword solutions for the term 'MAKE A SUMMATION' are ADD, which is a three letter word. ADD stands for 'to join or unite (one thing to another) so as to increase the size, quantity, quality, or scope of the first'. It is used in mathematics to ADD two or more numbers together, and it is also used in everyday language to describe the act of combining two or more things. In this context, the term 'MAKE a SUMMATION' could refer to the act of adding up all the elements of a set or group in order to come to a conclusion or total.