I’ve often seen ‘neighbor kid’, and I believe I may have seen ‘neighbor dog’, but I can never recollect seeing neighbor qualifying anything else, e.g. house/garden/car/man/woman/husband/wife. In those cases it’s always “neighbor’s”.
Is is only used as an adjective with very specific words or is that just an observational anomaly on my part?
It is a colloquialism or journalistic shorthand used in that way. It should really be ‘my neighbour’s kid’ etc. Neighbourhood kids would be all right too.
English has a remarkable tolerance for words to “borrow” part-of-speech status.
This is analogous to, say, “My milkman brother gets up early”. It occurs so regularly (even if counter-pedantically) that a listener has no problem making the mental adaptation and interpreting the construction as intended. Which is the whole purpose of a well-functioning language.
I don’t see it that way. If you say neighbor’s kid, that implies that the parent is a neighbor, but the kid is not.
To me “neighbor kid” is a neighbor who happens to be a kid. Kid modifies neighbor.
We use nouns as adjectives a lot, even in places where possession is implied. “Car door” is the same as “car’s door”, since the car possesses the door. The latter doesn’t get used as much (I would guess) since A) it’s clunky; the possessive “s” just begs to be elided; and B) possession is not always intuitively attributed to inanimate objects.
I suspect that our sense of the grammar tries to avoid possession of humans by humans, though, unless it’s important to the sense of the sentence. “Neighbor kid” is just a kid who happens to be a neighbor. “Neighbor’s kid” is the kid whose parents are neighbors, which semantically matters if you’re discussing who you will sue for the damage the kid did to your garden and sliding glass door and your pet Yorkie. :rolleyes:
This is called “attributive” use of the noun and is absolutely standard in English. Once in a garage I saw a card of plastic tabs called “brake shoe adjusting screw hole cover”, 5 attributives in a row.
There is a way to tell an attributive from an adjective. Unless stressed for particular emphasis, ordinary adjectives are less strongly stressed than the nouns they modify, while attributives are more highly stressed than the nouns they modify. The point is well illustrated by the phrase “French teacher”. Native speakers (at least Americans and Canadians) understand without it being mentioned that “FRENCH teacher” refers to a person who is teaching the language French, while “French TEACHER” refers to a teacher who happens to be from France. In the latter phrase, “French” is just an ordinary adjective. An amusing oddity of this example is that the noun “French” is actually an adjective used substantively. But that doesn’t affect the phonology.
Note that in “neighbor kid”, the “neighbor” has a stronger stress than “kid”.
I became aware of this in the spring of 1964 when someone wrote an instant book called “The Lyndon Johnson story” and the reviewer in the NY Times Book Reviews began his (rather negative, IIRC) review by saying pompously that he objected to the title because “In English, we don’t modify a noun with a noun.” I thought about it and realized that the fact that we do modify nouns with nouns is actually one of the characteristic features of the English language. I don’t know what rock this guy had lived under. Later on, I learned the word “attributive”.
Similarly, I live near “Wolf Trap Farm Park.” 
Yes, as OED confirms neighour has been used as an adjective in English for centuries although it does say that the usage is chiefly American and Irish now. It’s still certainly not unknown in British English though.
What RedSwinglineOne said - “neighbor’s kid” means that the kid is the possession of your neighbor. “Neighbor kid” says that the kid himself is a neighbor.
With house/garden/car, those are possessions, so it’s correct to say “neighbor’s car.”
With husband/wife, saying “neighbor husband” would be saying that the person is your husband but also your neighbor. Saying “neighbor’s husband” is also a little confusing, because it implies that this person is the husband of your neighbor but not himself your neighbor. Which could be the case, but unusual.
Perhaps we should ask Mr Language Person to weigh in on this.
Your welcome.
I’ve used “neighbor dads” as shorthand for “the male parents of young children who lived in the row houses in our block” in describing an annual ritual they performed.