What is once every 2 years called?

Biennial, a term often encountered in various contexts, denotes an occurrence or event that takes place once every two years. This adjective is aptly applied to describe activities or events that have a periodicity of two years.

In the realm of sports, the biennial chess tournament stands as a prime example of this concept. It signifies a chess competition that is held on an every-other-year basis, drawing participants from around the globe to compete for the prestigious title.

To clarify further, if we consider a hypothetical biennial chess tournament that last took place in 2015, the subsequent edition of the event would naturally follow in 2017, adhering strictly to the two-year interval.

Conversely, the term "biannual" carries a distinct meaning, referring to something that occurs twice a year. This terminology is often used in reference to regular activities or events that have a six-month periodicity.

It is important to note the subtle but crucial difference between biennial and biannual, as their meanings are not interchangeable. Misusing one for the other can lead to confusion and misinterpretation of the intended frequency.