未満
みまん · miman · JLPT N2 · noun
less than
未 (not yet) + 満 (full) = not full up to the mark, so below it: less than
未 means 'not yet' and 満 means 'full' or 'reaching a mark'. Together, 未満 marks a value that has not reached the threshold, so it is less than that number.
未 — tree 木 with extra short top stroke
未 originally pictured a tree with luxuriant new branches at the top, suggesting tender shoots not yet matured. From this 'not yet ripe' image it came to mean 'not yet' or 'have not.' It is also the 8th Earthly Branch, used in the traditional sexagenary cycle.