"work", "home" and "school" can be uncountable and be used without an article. What does make them so special? Are there other words like them?
In other words, why do I have to say "I'm going to the gym/uni"? But I don't need "the" for home/work/school.
The three words "work", "home" and "school" are all special because they can be used without articles where grammar normally requires one. They're actually part of three different sets of words.
Membership in all the sets is arbitrary. That's to say, there's no rule to know whether a word is in that category or not. So it's just a historical accident that "home", "school" and "work" are in these three sets, but "house", "madrassa", and "office" are outside the sets, even though they have roughly the same meanings.
Set 1
Words like "school" are in one set of place nouns that allows them to be used without articles in certain places where other place nouns require articles. Without the article, the phrase indicates that the purpose for being at the place is to participate in the normal function of that place.
Victor went to a church (He went to a church building; no information about why)
Victor went to church. (He went to attend church service)
My sister is in the jail. (She's inside the jail building; no information about why)
My sister is in jail. (She's a prisoner)
I searched for a complete list but didn't find one. This is the most complete list I was able to compile.
"Hospital" is slightly different in that "Luke is in the hospital" is ambiguous, and can mean either that Luke is a patient, or simply inside the building. Context is required to make clear which is the case.
Set 2
There's a second set of nouns like "work" and names of activities. These are different from the first set in that they are not place names, and using an article before them is meaningless:
Shelly just came from work. (She was doing her job there)
Shelly just came from the work.(bad grammar or different meaning)
Andrew's at poker. (He's playing in a poker game)
Andrew's at the poker.(bad grammar)
Set 3
There are also some other place words like "home" and "downtown" that are considered adverbs or function as adverbs when used without an article. They don't have the same meaning of going somewhere for the intended purpose of that place, and it's either ungrammatical to use them with an article, or the meaning changes.
I'm going home. (adverb; simply indicates travel; no special meaning about the purpose of "home")
I'm going to a home. (noun; probably means a nursing home, old age home, home for foster children, etc.)
Harold lives downtown. (indicates a location)
Harold lives in the downtown.(bad grammar)
I do not believe that there is a hard and fast rule.
It may be that the article is more likely to be omitted if you are actively engaged in what is happening at the location.
A clue to this is sports. If you say:
"I'm going to cricket", that would usually imply that you were taking part in a match or practice.
On the other hand, if you say "I am going to the cricket", it generally means that you are going to watch a match.
That's not infallible, though, because we don't say "I'm going to café", even though we do actively engage in something (eating and drinking), there.
