Other forms: quarterlies
Something that happens quarterly occurs four times per year, like your family's quarterly visit to your grandparents' house in Florida.
Magazines that are published every three months come out quarterly — in fact, they're commonly referred to as quarterlies. For businesses, many things happen on a quarterly schedule, from the quarterly taxes they pay to quarterly reports sent to shareholders. Think of a year as consisting of four quarters; anything occurring once per quarter happens quarterly. The Latin root, quartus, means "the fourth."