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noun [countable]

half of a decade

'As far as actors are concerned, the first five years of the 2010s proved that you can't make it big unless you're prepared to get into the Lycra and stride around in front of the greenscreen. This has been the demi-decade of the superhero, coming alongside genres like sci-fi and fantasy.'

Guardian 5th January 2015

It's 2015, the notional midpoint of the decade in which we're now living, be it the tenties, tweens, teens, tennies, tens, or … the list goes on. Having struggled to agree on a quirky name to rival our description of the years 2000–2009 as the noughties, it seems we've gone back to basics for referring to the half-way mark between 2010 and 2019, using age-old affixation to arrive at the designation demi-decade.

having struggled to agree on a quirky name to rival our description of the years 2000–2009 as the noughties, it seems we've gone back to basics for referring to the half-way mark between 2010 and 2019

A demi-decade is a period of time considered to be equivalent to half a decade, roughly five years. Prototypically this milestone falls in years which end in the number 5, since the most common perception of a decade is the run of years ending in digits 0 to 9. In principle, however, a demi-decade could be represented by any year, e.g. 2007 in relation to the years between 2002 and 2011.

The word demi-decade, though perfectly transparent and useful, is yet to be acknowledged by mainstream dictionaries. It's an interesting example of a concept which seems completely obvious, but for which we've been slow to adopt a specific moniker.

Background – demi-decade

The term demi-decade began to appear more widely in early 2015 in the context of retrospective commentary (e.g. British film critic Peter Bradshaw's pick of the top 50 films of the demi-decade, see the citation above), though it pops up in other domains too (e.g. a 'demi-decade' day for alumni of a University of Oxford college). Though it has particular relevance in 2015, the word has been used, albeit pretty marginally, for a number of years as a reference to five-year intervals, and a trawl of the internet gives evidence for its occurrence as far back as 1824.

Demi- is a combining form originating from medieval Latin dimedius, meaning 'half'. In modern usage it also often means 'partial', or even 'inferior' as shown in a word like demigod (= a less important god who may be partly human). Despite its transparency, demi- is a surprisingly unproductive prefix in English which seems to have largely confined itself to French loanwords (e.g. demi-sec = 'medium-dry (wine)' and demitasse 'small coffee cup'). This is probably because English speakers have other options for expressing the same concept, such as the far more productive semi- (e.g. semi-detached, semicircle) or simply half- as a combining form in its own right, e.g. half time, half-hour, half-truth, and more recently half-birthday, an expression partly popularized by its appearance in J. K. Rowling's Harry Potter novels. The practice of celebrating a half-birthday (a day exactly six months before or after your birthday) has become more fashionable in the last few years, particularly for younger children with inconvenient birth-dates, and accordingly there's now plenty of evidence for expressions such as half-birthday party/cake/card, etc.

by Kerry Maxwell, author of Brave New Words

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This article was first published on 8th April 2015.

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a form of location that involves the underwater detonation of a bomb which causes sound waves that are picked up by ships

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