Complex sentence: Though they are often referred to as martini glasses, they differ from martini glasses in that they have smaller, narrower bowls with rounded or flat bottoms, while martini glasses generally have larger, wider bowls which are fully conical at the bottom.
Split into simpler sentences: Though they are often mistakenly referred to as martini glasses, they differ from a martini glass in a couple of ways. Cocktail glasses have smaller, narrower bowls with rounded or flat bottoms, where martinis generally have larger, wider bowls which are fully conical at the bottom.