Language point

Two million people gathered in the streets of Rome ... celebrating the Italian capital's second annual all-night cultural extravaganza.

When we describe events that take place regularly, we can use a phrase that describes exactly how frequently they take place.

Examples: The school organises a picnic once a year.

The English Club holds a meeting once a week.

However, sometimes we need an adjective, instead of a phrase, to describe the event.

Examples: I was sick yesterday, so I couldn't go to the school's annual picnic.