There are few things in sport as clear-cut as the distinction between opponent and team-mate.
As far as the rules are concerned, you try to beat the former, and try to help the latter.
Only in Formula One, and motor racing in general, is an athlete expected to beat and work alongside the same person - his team-mate.
In a sport where winning is determined by the machine as much as the man, the only true level playing field is between team-mates who drive the same car.
Or, as Red Bull's Max Verstappen put it: "Since I was four years old (when he began karting) you always try to beat your team-mate first, then you try to win the race."
The Dutchman was quick to add that he has a good relationship with team-mate Daniel Ricciardo, but his words also reflect the reality of F1 - there is no happily ever after for a pair of team-mates even, or perhaps especially, under the very best of circumstances.
Putting two of the best F1 drivers of the day on the same team and in the best cars may sound good in theory but has often proved a recipe for disaster when there is room for only one name on the winner's trophy.
FIRST THINGS FIRST
Since I was four years old you always try to beat your team-mate first, then you try to win the race.
MAX VERSTAPPEN, Red Bull driver, on his priorities.
Ayrton Senna's feud with fellow all-time great Alain Prost when the pair were at McLaren from 1988 to 1989 is the rivalry that has set the standard.
Senna, the young upstart joining a team at the top of their game for the 1988 season, quickly gained the upper hand on then two-time champion Prost.
But, when the Frenchman began to put the pressure on him late in the year, Senna responded at the Portugal Grand Prix by squeezing Prost towards the pit wall.
For sure on Sunday, everyone can be selfish to do better, but it helps if you understand the bigger picture.
DANIEL RICCIARDO, Red Bull driver, on how the relationship with a teammate can stay healthy.
Prost got past and claimed victory, but the duo's relationship was never quite the same after that.
"If Ayrton wants the championship that badly, he can have it," said a fuming Prost after the race.
Likewise, Mercedes' dominant car over the last three years set the stage for the sport's fiercest rivalry - between their two drivers, Lewis Hamilton and Nico Rosberg.
Once close friends and karting team-mates as teenagers, Hamilton was singing a different tune after a dust-up at the 2014 Monaco GP.
"We are not friends, we are colleagues," said the Briton then.
The famously taciturn and unflappable two-time world champion (1998-1999) Mika Hakkinen used the same analogy when he was in town this week.
"It's like when you're back in the office," the Finn told The Sunday Times. "There's going to be people you don't like but you just work with them and do your job."
Team-mates sometimes get in the way of each other doing the job, however, and even Hakkinen, who enjoyed a cordial relationship with David Coulthard during his title-winning years, had to deal with a collision with the Scot at the 1999 Austrian GP that sent him from pole to the back of the field.
In the most recent such incident, Force India driver Esteban Ocon accused team-mate Sergio Perez of trying to "kill" him during the Belgian Grand Prix last month.
The pair collided twice during the race, with the second instance seeing Perez sustain a right-tyre puncture and Ocon a damaged front wing.
"He's going to have a child. I don't know if he wants to die or something. It's just ridiculous," said Ocon at the time.
Force India decided to implement team orders after the race, with chief operating officer Otmar Szafnauer saying "if they can't sort themselves out then we'll have to do it for them".
Team orders refer to the practice of teams issuing instructions to drivers to drive differently against each other than they would against other drivers.
One driver may be asked to let his team-mate pass, for example, or both might be told to hold their positions so there is no risk of collision.
The International Automobile Federation (FIA) attempted to ban the use of team orders in 2002, but the sport's governing body retracted the ban in 2011 as teams were continuing to find ways around the rule.
Ricciardo, normally the most amiable of souls, proved he too was not exempt from the norm when he blew up at Verstappen at the Hungarian GP in May when the two collided, forcing the Australian to retire from the race.
The pair were back to laughing - and attempting to eat durians - together in Singapore, but the 28-year-old acknowledged that the relationship between F1 team-mates is balanced on a knife-edge.
"If you work together the team can become stronger and grow. For sure on Sunday, everyone can be selfish to do better, but it helps (with the relationship) if you understand the bigger picture," said Ricciardo.
"It's a tricky spot (to be in). Everyone manages it differently. Lewis and Nico managed it their ways. I don't think that was very helpful for any of them, but everyone has his own way."
•Additional reporting by Ho Cai Jun and Ian Kiew