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"La ciudad" is a form of "ciudad", a noun which is often translated as "city". "La avenida" is a form of "avenida", a noun which is often translated as "avenue". Learn more about the difference between "la ciudad" and "la avenida" below.
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (settlement)
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).