Looking for a single word that describes "up to but not including x" where x is a number [closed]
In most numerical contexts we use "less than". That's two words, not one, but it may work for you.
Below is an obvious one-word answer (I have to write more 'cos it's below the minimum length!).
"Under", meaning "less than", is only one word. Under X.
For the numbers coming before but not including, I think you could say:
preceding X.
preceding: Existing or coming before another or others in time, place, rank