In the US, an address can, in general, be almost anything that the land-owner intends. In areas with a municipal government (such as NYC) addressing may need to

In the US, an address can, in general, be almost anything that the land-owner intends. In areas with a municipal government (such as NYC) addressing may need to be approved by the municipal planning authority, but this isn't always the case. The USPS will often not deliver to an address until the local postmaster has entered it into the postal service database, but in some cases, esp. in urban areas, they'll deliver mail without this if the address is similar enough to a nearby property that it gets to the right letter carrier route (e.g. a 1/2 or B unit if USPS knows about the base address). The point of this is that addresses like 1/2, and even 3/4 and so on, do occur in the US, although they're uncommon compared to alphanumeric addresses. If you're in the position of dividing a housing unit it's a better idea to use a B suffix, I used to deal with a 1/2 address and it was constantly rejected by online forms that didn't allow a / in that field. The USPS has long angled to reduce these problems by assigning a unique number to every delivery point (the ZIP + 4 + DP or '11 digit ZIP'), but this is complicated for all of the reasons you would imagine. Fundamentally the job of interpreting an address still comes down to the common sense of the letter carrier. USPS P28 has extensive information on how USPS recommends that software handle address formats for e.g. bulk mailing, which is rather lengthy in part because of the huge variety of address variations present in the US.