Many (most?) sources define "biannual" only as "twice a year". Yet Merriam-Webster says: "Some people prefer to use semiannual to refer to something that occurs twice a year, reserving biannual for things that occur once every two years."
It's a good lesson for contract writers and anyone else that wants to be clear. Never use any of those terms. Instead, write, "Inspections will be done every 24 months", or, "The toner needs to be ordered every six months".
If something is supposed to occur every other Friday? Write it just like that, or "every 14 days". Don't say, "Paychecks are distributed bi-weekly"
Say you've got a 10 new joiners per week at your high-turnover packing factory, and a sign outside the admin office that says "Paychecks are distributed bi-weekly".
Maybe typically 5 of them have had a job before in the area, 3 have had a job elsewhere and 2 have never had a job. Not all of them have the same level of education.
How many will misunderstand your sign? Might any of those misunderstandings about money cause problems for people?
Considering the comparitive cost of writing the sign as "every two weeks", and the reduction in potential confusion, it seems like a no-brainer to write it that way.
I mean are you talking about jobs meant for those with some kind of college education, or are you talking about jobs aimed at (say) middle-school drop-outs? For the latter, I can see it, but for the former it's almost insulting to try to simplify things too much just in case the employee doesn't have common sense that they will need on the job anyway...
[1] http://writersrelief.com/blog/2011/05/biannual-biennial-or-s...