The Greek Letter With Two Shapes

The Greek letter sigma changes its shape depending on where it sits in a word. While σ appears at the start or middle, a totally different form, ς, must be used only at the very end.

This rule is surprisingly strict, acting as a visual marker to show exactly when a word reaches its finish. It functions much like how we use capital letters to signal the start of a sentence. Because of this, a name like Odysseus contains two different versions of the same letter. It is a rare example of a simple character having a specific identity tied to its position in a sequence.