Which word does NOT belong with the others? rye, sourdough, pumpernickel, loaf

Given data

• Word list: rye, sourdough, pumpernickel, loaf.

Concept/Approach
Three are bread types; one is a shape/quantity of bread.

Step-by-Step reasoning
Rye – bread made with rye flour (type). Sourdough – bread using a fermented starter (type). Pumpernickel – dark rye bread (type). Loaf – a form/quantity (a whole unit of bread), not a specific recipe.

Verification/Alternative
One can bake a loaf of rye, a loaf of sourdough, etc.; 'loaf' describes format, not variety.

Common pitfalls

• Assuming 'loaf' is a flavor; it is a shape/unit.

Final Answer
loaf