Final answer:
The fundamental difference between elliptical and spiral galaxies is that elliptical galaxies lack the disk of a spiral galaxy and consist mainly of old stars with little ongoing star formation, compared to spirals which contain both old and young stars and have continuous star formation.
Step-by-step explanation:
The most basic difference between elliptical galaxies and spiral galaxies is that elliptical galaxies lack anything resembling the disk of a spiral galaxy. Elliptical galaxies feature shapes that are spheres or ellipsoids, containing mostly old stars, with little to no current star formation. In contrast, spiral galaxies have a distinctive disk structure, with younger stars and ongoing star formation.
Spiral galaxies are characterized by a combination of older and younger stars, as well as the presence of gas and dust that contributes to star formation, which can occur over the entire lifetime of the galaxy. They tend to evolve in a way that involves several distinct phases over a long period. Elliptical galaxies, on the other hand, formed most of their stars early in their history, with star formation occurring rapidly and then ceasing, resulting in a population of older stars and very little interstellar matter. The structure of ellipticals ranges from nearly spherical to slightly elongated shapes.