It's true that electrons are very small and their mass is tiny compared to things we encounter in everyday life. But they definitely have mass, and it's a fundamental property of them. Here's why:

* They have inertia: Electrons resist changes in their motion. This resistance to acceleration is a direct result of their mass.

* They contribute to the mass of atoms: Electrons are part of atoms, and their mass is a factor in determining the overall mass of the atom.

* They have a measurable mass: The mass of an electron has been carefully measured and is known to be approximately 9.10938356 × 10^-31 kilograms.

So, while electrons are incredibly light, they do have mass!