I was inspired by this awesome puzzle. Here is an image of a word tree borrowed from there:
In a word tree every path from the root to the leaves must form a distinct word. The size of the tree is the number of distinct words it forms in this way. The size of this tree is 16 as it forms 16 distinct words: BLOOM, BLOOD, BLOWN, BLOWS, BLAND, BLANK, BLASÉ, BLAST, BROOK, BROOM, BROWN, BROWS, BRAID, BRAIN, BRASH, BRASS. Note that words that do not reach the leaves are not counted, so for example we do not count the words BLOW, BROW and BRA. You must use words from this dictionary. Every branch must split into exactly two (or zero) other branches above it. The two branches may use the same letter. The leaves can be at different distances from the root. So we can extend the BRAIN branch into BRAINY and BRAINS, thus increasing the size of this tree to 17. What is the size of the largest word tree possible? You may use a computer to find the answer.