Twig. A word often overlooked in the English language; aptly defined as a "slender woody shoot growing from a branch or stem of a tree or shrub," whose uses throughout history have remained unchanged. For that, it's significance is almost unparalleled.
EDIT: Upon further research apparently twig has other meanings as well. Most notably so, as pointed out by Google: "to understand or realize something." Example: "it was amazing that Graham hadn't twigged before."
Which leads me to believe that the third meaning of twig is actually to describe a new age drug, to which the previous sentence remains a good example of how to use it in a sentence.
Poor Graham, all of the kids at school always used to tease him for being too pussy to twig.