The triangular inequality theorem says the sum of two sidesof a triangle is greater than the length of the third side.
lets assume the lengths of the sides of your triangle are A, B and C
if we take the triangular inequality theorem A < B + C
if we subtracted B from both sides we would get
A - B < C
now if we want to generalize this you could say that the length of C (the third side) is larger than the difference between the other two sides (A and B)