What is the defining characteristic of a barred spiral galaxy, such as the Milky Way?

Answer

It possesses a distinct, elongated bar-shaped structure passing through the center

Barred spirals, designated 'SB', possess a distinct, elongated bar-shaped structure made of stars that passes through the center, from which the spiral arms emerge.

What is the defining characteristic of a barred spiral galaxy, such as the Milky Way?
classificationgalaxiesastronomyproperties