While thumbnail definitions are great for textbooks, applying them to real engines is another matter. One concern is that every car engine has an idle-to-redline operating range. For example, the Dodge Challenger’s 6.2-liter Hellcat V-8 produces 707 horsepower ONLY at 6000 rpm. It makes substantially less power at idle (only enough to spin engine-driven accessories) and a bit less than 700 horsepower at the 6200-rpm redline. And it delivers its maximum 650 pound-feet of torque ONLY at 4000 rpm.
PS (pferdestärke), CV (chevaux vapeur) or DIN metric horsepower are exactly that – an attempt to make horsepower metric. A metric horsepower is the equivalent of 0.986 horsepower – this is why the Volkswagen Golf R is advertised with 300PS but only has 296hp. Equally, 300PS sounds better than 296hp simply because it’s a bigger number