The recruitment industry is very fond of Latin phrases, yet no one can explain why. Job adverts and job specifications frequently use Latin words like “per,” “circa,” “pro,” “annum,” “diem,” “rata,” “bona” and “fide.” Those words are not short cuts, because each represents just one English word that would be just as easy to write. The simple fact is that it has become a tradition in recruitment to use a few Latin words and they are unlikely to ever stop doing it.
“Per” means “each” and is so well integrated in to the English language, that no one can criticise the recruitment industry from using it. You look at the price of petrol “per gallon” or “per litre.” The usage of this small Latin word in everyday English is so extensive that nobody notices its ancient and foreign roots. You might calculate a per cent or walk three miles per day, without wearing a toga.
Although “circa” is not a commonly used as “per” it is, none the less, one of those small Latin words that comes into everyday speech. However, it is particularly prevalent in use for dates and salaries. “Circa” means “about” and although it would not be any more effort to write the English word instead, “circa” is still in regular usage in the UK.
It is unlikely that you will ever see “per circa” as a phrase. This combination has never slipped into general usage and if you ever see this phrase in a job advert, it is probably a typo. You will see an advert advertising a pay rate “per hour,” “per day,” “per week,” “per month” or “per year.” Curiously, the recruiters seem prepared to use the Latin “per” with a wider range of timings in English than in Latin. Only the Latin for “day” and “year” are used to describe salaries -- “per diem” and “per annum.” Of these “per annum” is the most frequently used for salaries, with “per diem” being used more for expenses. "Circa" is regularly used in job adverts to give an indication of a salary being offered without giving a cast iron commitment that you will be offered exactly that level of salary. An advert that offers “circa £30,000 per annum” may attract people who would accept £27,000 a year in order to price themselves into a job, or that job could go to someone whom the recruiter is prepared to pay £33,000 a year.
There is a movement to eradicate these phrases from general usage in the UK. Local councils including Bournemouth, Salisbury and Fife Councils have banned the use of Latin words in all communications with the general public. Job seekers should not get too upset about the expectation for them to understand Latin in order to apply for a job because the standard response to that advert is to send in a Curriculum Vitae.