ARCS, COURS, AND MGW SERIES

To begin with, MGW is a three-letter acronym that here stands for Magical Girl Warrior; series (most often anime, though there are also Western/animesque versions) starring a diverse ensemble cast of girls -from kid childhood to young adulthood- battling sinister forces that threaten the peace of the multiverse.
Naoko Takeuchi codified the genre and defined its defining characteristics in her Sailorverse (Sailor V, Sailor Moon, Sailor Moon Crystal), which blended the classical magical girl tropes with some Super Sentai characteristics like a team of different heroines with balanced abilities and personalities. The result was a series simultaneously aimed toward and empowering to girls with large amounts of character building and storyline that still gave focus to the battles and allowed for fanservice. A virtually-unheard-of combination at that time, the series quickly attracted a rabid fanbase with a ridiculously-wide demographic. While many early anime of the genre which followed were accused of being (and often were, at the start) rip-offs of Sailor Moon trying to repeat its success by copying the formula, eventually they evolved into unique works and a novel hybrid genre, going From Clones to Genre.
Now this article is about anime in general, the term "arc" as used in this blog, and the equivalent Japanese term "cour" ("kuuru" in katakana).
Since Kirakira Precure à la Mode has reached its arc finale and segued into a new arc this week, I thought that the opportunity to talk about anime cours could not be missed. For each and every story arc of a Pretty Cure series fits exactly into a cour of the same series: now, to put KKPCàlM as an example, as the Winter Cour ends and the Springtime Cour begins, it has brought us the wrap-up of the Debut Queue arc and the first episode of the Giulio arc. The Debut Queue arc lasted all Winter Cour long, while the Giulio arc will encompass the whole Springtime Cour.

Noun
Cour ‎(plural cours) | IPA: /kuʁ/
a three-month unit of television broadcasting
a portion of a television program aired over the course of one such period

Etymology: From Japanese クール (kuuru), from French cours. Attested in English among the anime community from at least 2007.

The word cour is used to measure the length of an anime series. In general, a single cour has 10 to 14 episodes that run during a three-month period that coincides with the seasons. That’s why one cour belongs to either the Winter, Spring, Summer, or Autumn season.

Winter Season: January, February, March
Spring Season: April, May, June
Summer Season: July, August, September
Autumn Season: October, November, December

Episodic anime are usually broadcast as either a single cour (most common) double cour, or split cour:

Single Cour: 10 – 14 Episodes
Double Cour: 24 – 26 Episodes on two contiguous seasons (e.g. Spring – Summer)

Split Cour: 24 -26 Episodes. The second cour is broadcast after a season off (springtime-autumn or summer-winter).

Why are anime broadcast in cours?

In just one word: Convenience. Creating an anime in single cours instead of full-blown 24-episode runs (or more) leaves the production company with more options. If the first cour is popular and the ratings are good, then they can follow up with a second cour back-to-back. If the fans like the show but there are certain complaints that need to be addressed, the series can go to the split-cour format and skip a season between the first and second cour (see how convenient is the use of cour and season here?) If the show is a total flop, or if the ratings are not promising, the company can conclude the show and start working on something new.

Definition¹

cour [koor]
noun

1. One of the four conventional three-month periods of television broadcasting in Japan (January to March; April to June; July to September; October to December): "Noragami" aired during the first cour of 2014.
2. A portion of a television program aired over the course of one cour₁: The big reveal at the end of the first cour of "Valvrave" had me on the edge of my seat!

Usage

I'm really not sure how long "cour" has had currency in English. There are attestations from at least as early as 2007.² I think that's not too long after the term began to see usage in English-speaking anime communities, but I could very well be mistaken.

This term was probably quickly adopted because it provides an unambiguous way to refer to a roughly 13-episode block of episodes, by contrast with "season", which (as seen here) can mean many different things in different contexts.

A cour is not of precisely-defined duration, and can, in practice, last anywhere from 11 to 14 weeks (and hence, the same number of episodes), though 12-13 weeks is most common, since a 52-week year cleanly divides into four 13-week subunits (or perhaps 12-week subunits with a week off in between).

Etymology

This usage of the word "cour" in English is (perhaps surprisingly) a borrowing of the Japanese word クール (kuuru), which means essentially the same thing as the English "cour".

Japanese kuuru is itself a borrowing, though the language of origin is not known with certainty. The most popular hypothesis is that it derives from French cours, cognate to "course" as in "lecture".Note that the English "cour" is effectively a back-formation from cours (which is singular in French), and the singular/plural distinction between "cour" and "cours" is an English innovation.

In any case, the path "cour" took on its way to English is decidedly opaque, and so it is no surprise that it doesn't show up in English dictionaries.

WHAT DOES COUR MEAN?

Cour is a word used to describe a span of anime episodes during their initial Japanese TV broadcast. One cour runs for three months and typically consists of anywhere between 10 to 14 episodes and sometimes will contain a full season if the season is short enough.

HOW IS A COUR DIFFERENT FROM A SEASON?

A cour is essentially one production block of episodes that may or may not have a break in between it and the next block.

An anime cour really isn’t any different than saying, “A batch of anime episodes” or “The first/second half of an anime season.” Each three-month cour block in Japanese broadcasting is fairly defined however with each one starting in the months of January, April, July, and October and often named after their starting month or correlating season.

Example: The first cour of the year can be referred to either as 1月クール(Ichigatsu Kuru / January Cour) or 冬クールFuyu Kuru (Winter Cour) or even 第1クール (Daiichi Kuru / Cour 1).

WHY ARE ANIME SERIES PRODUCED IN COURS?

Planning an anime series in a cour rather than a full-blown season provides the production team and the broadcasters with a more flexibility. For instance, if a show airs one twelve-episode cour and has good ratings, the show runners may elect to produce another cour as a follow-up.

On the other hand, if the first cour airs and it doesn't perform well, then the show can be considered concluded (i.e. not renewed), and the production team loses less money by continuing to work on a less-profitable show.

WHERE DOES THE WORD COUR COME FROM?

The original Japanese word is クール, which is pronounced kuuru (funnily enough, the same spelling and reading as cool when using the English word in Japanese). It is thought to come from the French word cours which means lecture or course and it can be easy to see how the word could have been reinterpreted in much the same way we have in English when discussing meals. We two-course meal, ​meanwhile in Japan they can enjoy a two course anime series. Sometimes if it’s extra popular, the cooks may even make an extra course!

It’s a bit of a mystery as to why some of the English language anime fandom is using the word cour over kuru. It’s possible they’re referencing the original French origins of the word.

4 COUR (50-54 EPISODES, CONTINUOUS, OR YEAR-LONG SERIES) EXAMPLES

The Pretty Cure franchise; each and every continuity is a 4-cour or year-long series, always beginning in midwinter and wrapping up around Christmas.

AND NOW FOR THE ISSUE TO WHICH ALL THIS EXPLANATION BOILS DOWN:

COUR

vs.

ARC: 

Since each cour of a Precure season contains one story arc within its 12-13 episodes, each narrative arc overlapping with a different cour (for instance, the Twilight arc of Go!Princess Pretty Cure overlaps exactly with the Springtime Cour of said series), the terms "cour" and "arc" can be used interchangeably, even though "cour" refers to the production and "arc" refers to the narrative of a batch of episodes.