dot, tick or dot radical (no. 3)
丶 is a single dot or tick mark. It is primarily used as a radical component in other characters, where it often represents a small mark or a drop.
丶 is a simple pictograph of a dot or a small mark. Its form has remained essentially unchanged as a single stroke.
Picture a single drop of ink falling onto paper, leaving just one small dot. That dot is 丶.
For チュ, imagine the dot is a tiny chew mark left by a small animal: chew -> チュ, and the mark is just a dot.
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