...without the need for n+1" Says Anth.
There have been various threads on here about n+1.
Various discussions about 'permission to buy new bike', storage space etc.
I think there was (almost) a consensus that you 'need' two (especially if you cycle to work) for when you've got a puncture.
Not sure if anyone has done a list.
You don't need ALL.
The 'do everything bike' - with panniers, towing hitch and kid's seat.
The 'reliable get me where I need to go bike' - puncture proof(ish) tyres, not too many gears that might go wrong etc.
The racer (aka road bike) - pose or serious.
The tourer - day or distance.
The fixie - pose or 'it's all you need really'.
The singlespeed - as above but less 'full-on'.
The folder - for busy train routes. (Subset "Brompton" - may or may not be a fetish object.)
The cargobike - when a trailer won't do.
The classic - bit like an old car (usually in bits).
The retro - 'it's so cool'.
The Chopper (or similar) - 'I had one when I was a kid'.
The 'mountain bike' - never sees a mountain.
The Mountain Bike - for serious off-road use.
The downhill Mountain Bike - for very serious off-road use.
The recumbent - apparently some people think they are 'the only sort of bike' aka 'invisible bike'.
The recumbent tricycle - apparently a smaller number of people think they are 'the only sort of bike'.
'Ordinary' tricycle - not just for those with no balance.
Ordinary aka penny farthing.
Tandem - for people with close friends.
BMX - trick or transport.
Special sport - Polo, Speedway etc.
Track (not to be confused with "fixed" - which should have a front brake to be street legal.)
Ornament - should/does hang on wall.
Other.
Some of the above may be interchangeable. Most have subdivisions.