What is the hybridization of oxygen in furan?
Furan is aromatic because one of the lone pairs of electrons on the oxygen atom is delocalized into the ring, creating a $4n+2$ Hückel aromatic system.

The steric number is sometimes incorrectly described as the sum of the number of sigma bonds and the number of lone pairs. However, it is more accurately given by the number of sigma bonds plus the number of localised lone pairs.