Exactly how often is that?

Even if you decide to make a firm distinction between bi- and semi-, these words are used so interchangeably that it’s still confusing.

In a Word

I was researching plants to put in my garden this spring and was surprised to discover how many common vegetables are biennials. They have a two-year growth cycle, producing flowers and seeds after overwintering. Carrots are in this group, as are kale, parsley, onions, broccoli, celery, and beets. 

The definition of biennial is pretty clear. When applied to nonvegetation, it means “occurring every two years,” like the art exhibition that takes place in Venice, Italy, the Biennale. Biannual, in contrast, means “twice yearly” – a biannual sale happens twice a year.    

Other bi- words can be confusing. Paul Beatty’s novel “The Sellout” features a club that meets bimonthly. The meetings, Beatty describes, “consisted mostly of the members who showed up every other week arguing with the ones who came every other month about what exactly ‘bimonthly’ means.” The truth is, bimonthly is ambiguous, with no “correct” definition.

The same goes for biweekly. In American English, this generally indicates “every two weeks,” but in British English it more commonly refers to something that happens twice a week. If you say “The paper comes out biweekly,” it’s not clear whether it appears every Tuesday and Friday or every other Monday.

If you want to be more precise about timing, the Latin prefix semi- might serve. While bi- means “two,” “twice,” or “doubly,” semi- indicates that a given unit of time is halved. So a semiannual sale happens once every half a year – just like a biannual one. A semimonthly publication comes out twice a month.  

British English has another useful term for “every two weeks:” fortnightly, a fortnight being 14 days. This sounds odd in American English and is becoming less common in Britain as well. Perhaps the least practical semi- word comes from the Victorian Era, when it was occasionally employed to refer to the timing of tides: semimenstrual, mensis being the Latin word for “month.”   

Even if you decide to make a firm distinction between bi- and semi-, these words are used so interchangeably that it’s still confusing. If you really want to be clear, it is probably best to be less concise and simply say “once a week” or “twice a month.”

I’m glad this column is hebdomadal (from the ancient Greek word for “seven”) – once a week. It’s so much simpler.