That's not correct. Not every subnet is a /24. Further, you don't necessarily need a network and broadcast address for a subnet. That's a local issue. See IETF RFC 3021 for one example of not having a network and broadcast address.
it's the network address only if you define your network as a /24 . if the mask is different it could be a completely valid address.
:facepalm: right, of course, makes sense. Thanks.
0.0.0.0 is a "network" address no matter how many bits are in the netmask. Having said that, there really isn't a use of "network" addresses (especially as distinct from broadcast), apart from the convention being baked into basically everything.