Here's why:

* Color: The Sun appears yellowish-white to us, but it actually emits most of its light in the green part of the spectrum. This puts it in the "yellow" category.

* Size: The Sun is a relatively small star, considered "dwarf" in size compared to giants and supergiants.

* Spectral Type: Astronomers use a system of spectral types to classify stars based on their temperature and composition. The Sun's spectral type is G2V.

* "G2" indicates its temperature, which falls within the "yellow" range.

* "V" indicates it's a main-sequence star, meaning it is currently fusing hydrogen into helium in its core, like most stars in the universe.

So, while we often just call it "the Sun," its official classification is a yellow dwarf.