The first expression
is 0 when a=0 and increases by 1 each time a increases by 0.001. So it's floor(1000a) which, given all the Roman numerals, I should probably write as $\lfloor Ma\rfloor$.
The yellow square
is about 0.61 times the size of the white one. Perhaps this is hinting at the golden ratio (often written $\varphi$ or $\tau$) but there might be some further thing I'm missing.
The fraction at the end
is probably "voltage, in volts, over resistance, in ohms", yielding "current, in amps" or $I_A$.
So perhaps we are looking at
$\lfloor Ma\rfloor\varphi I_A$ or the Mafia. Eek! (The Mafia would fit quite well with the two earlier answers of PIZZA and SECRET, of course.)
[EDITED to add:] OP indicates that I don't have the intended interpretation of the yellow square, so here is another possibility:
In WYSIWYG equation editors, you often see something very much like this (though much smaller) to indicate a subscript. E.g., this is what the relevant menu item in Word's equation editor looks like: and this is what you get when you move your cursor into the subscript: . In that case, this could indicate SUB, making our final answer MASUBIA, the name of a group of people in central Africa.
if, as above, it's denoting a subscript, perhaps we should replace it with something that commonly appears in subscript position. The most obvious things would be $i,j,k$ but none of those makes a word -- but $n$ yields MANIA, which seems at least kind possible.
I confess that neither seems terribly likely.