Main Difference
The main difference between Capellini and Vermicelli is that the Capellini is a Type of pasta and Vermicelli is a type of pasta
Capellini
Capellini (Italian pronunciation: [kapelˈliːni], literally “little hairs”) is a very thin variety of Italian pasta, with a diameter between 0.85 and 0.92 millimetres (0.033 and 0.036 in). Like spaghetti, it is rod-shaped, in the form of long strands.
Capelli d’angelo ([kaˈpelli ˈdandʒelo], literally angel hair — hence, “angel hair pasta” in English) is a thinner variant with a diameter between 0.78 and 0.88 millimetres (0.031 and 0.035 in). It is often sold in a nest-like shape. Capelli d’angelo has been popular in Italy since at least the 14th century. As a very light pasta, it goes well in soups or with seafood or light sauces.
Vermicelli
Vermicelli (Italian: [vermiˈtʃɛlli], lit. “little worms”) is a traditional type of pasta round in section similar to spaghetti.
In Italy vermicelli is slightly thicker than spaghetti, but in the United States it is slightly thinner.
The term “vermicelli” is also used to describe various types of thin noodles in Asia.
Vermicelli (noun)
Long, slender pasta, similar to spaghetti, only thinner.
Vermicelli (noun)
Any type of long, thin rice vermicelli.
Vermicelli (noun)
pasta in the form of long slender threads.
Vermicelli (noun)
shreds of chocolate used to decorate cakes or other sweet foods.