Smaller
Not so much, smaller, shorter, fewer, not so great, slighter, and reduced.
Under
A smaller amount, not as much as, below, not so much as, under, and shy of.
Rarely
To a lesser degree, not so much, rarely, little, to a smaller extent, not as much, barely, and not much.
Minus
Minus, excepting, lacking, subtracting, and without.