means to break into smaller parts like when fruit rots or
decomposes. Decomposing a number
means to break apart a number into to smaller
numbers. 5 can decompose, or
break apart, to 4+1 or 3+2. It can also be decomposed into
3 or more addends (the numbers being added):
1+1+1+1+1 or 1+1+1+2 or 1+1+3 or 1+2+2.