Bi-Monthly (once every two months)

Question

Definition from Oxford language

Bi-Monthly: done, produced, or occurring twice a month or every two months.

How can I ensure it is correctly interpreted as every two months instead of twice a month? I am thinking of a single word instead of a phrase.

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EDITED:

Thanks everyone who weighs in. As a non-native English speaker and a new learner, I find it strange that bi-monthly can mean once every two months and twice per month.

Let's say if someone says you will be billed bi-monthly or you have to make a payment bi-monthly How will it be interpreted if no context is given?

I am writing a list like below

• Monthly
• Bi-Monthly
• Quarterly
• Bi-Annually
• Annually

If no context is provided, I believe it is understandable that bi-monthly means once every two months.

However, if I were to rearrange the list like this

• Bi-Monthly
• Monthly
• Quarterly
• Bi-Annually
• Annually

It will be interpreted as twice per month although what I want to mean is actually once every two months.

Answer 1

According to an article in the LA Times, the ambiguity exists more in theory than in practice, since if you refer to being paid bi-monthly, people will interpret it as meaning twice a month, whereas if you refer to a publication being released bi-monthly, people will interpret it as meaning once every two months:

Fascinatingly, it seems no one got confused by these two different meanings of the prefix “bi-.” When a worker who got paid every 15 days said he was paid bimonthly, everyone knew what he meant. And when the same worker said his magazine that arrived six times a year was “bimonthly,” everyone knew what he meant. (LA Times)

It goes on to say, quoting Merriam-Webster's usage guide:

“In the publishing world,” reports the usage guide, “everyone assumes you know ‘bimonthly’ means every two months. … On the other hand, we have evidence that in the world of education, ‘bimonthly’ usually means ‘twice a month.’”

Still, if you want to avoid ambiguity entirely, you can't use "bi-monthly".

"Two-monthly" would unambiguously mean "every two months", but isn't particularly common.

"Fortnightly" unambiguously means "every two weeks" (which isn't necessarily quite the same thing as twice a month, since most months are slightly longer than four weeks). "Fortnightly" is a rare word in the US, but is very common and well known in the UK.

Answer 2

There is unfortunately no unambiguous single word for this. The best you can do is "every two months" or "every other month."

As you noted, "bi-monthly" can be taken to mean either twice a month or every two months. "Semi-monthly" unambiguously means twice a month. The same trouble exists with biennial, biannual and semi-annual. In my opinion this is the result of sloppy usage and education, but the ambiguity is pervasive enough that it's a fact we have to deal with (as you can see in the dictionary definitions).

For other time periods, there are sometimes unambiguous options, like quarterly for every 3 months or fortnightly (uncommon) for every 2 weeks.

Answer 3

The confusion primarily exists among those who have had no reason to learn the difference between the two. For example, you are 17 years old and have never received a paycheck. When I was 17, I misunderstood Bi-Monthly to mean twice a month.

• Bi-Monthly - Every two months. If you receive a paycheck on Jan 1, March 1, May 1, etc., you are being paid Bi-Monthly. Almost no one is the U.S. is paid Bi-Monthly. As others have said, Bi-Monthly is mostly seen in periodical distribution frequencies.
• Semi-Monthly - Twice a month. In the case of paychecks, usually spaced as evenly as possible within the month.

People should be expected to know this. In the U.S. this is standard. Of course, there are those who don't know this. Explain it to them if you have a chance.