Particle は is often called topic, emphasis, contrast, etc. particle. Can particle は use cases be summarized by a single term disambiguation? If one could think of は as disambiguation particle should one ever need to remember all sub-cases?
According to Michiel "Pomax" Kamermans in the section titled Essential Particles, the particle は should be thought of as disambiguation particle.
Quoted from chapter 220.127.116.11 — は — Disambiguation:
As already explained in chapter 2, in the verb particle section, は (pronounced わ) is used to disambiguate statements. Let's look at what this means in terms of what は does, compared to を or が. Imagine that we're having a conversation and we're talking about watching films in the cinema, DVD rentals, and TV shows, and the following sentence is used:
Where for (...) we either find が, を or は. While all three would translate to "(I) watch TV a lot", their connotations are very different.
When we use を, the sentence is fairly plain information. Whoever of us says it wants to convey that they watch TV a lot, and nothing more.
When we use が, the sentence is still plain information, although using が rather than を emphasises that whoever is talking about TV, is talking about TV. This using が as an emphasis marker is a fairly common practice, although you need to know why you're emphasising, of course.
By using は, everything has changed. The speaker has indicated that the information in the sentence requires disambiguation in terms of what it applies to. In this case, the "watching a lot" only applies to TV. While を and が told us only one thing, namely the plain information that TV was being watched a lot, は tells us two things. First, the basic information, that someone watched TV a lot. However, because the speaker felt they needed to make sure that we know it only applies to TV, it also tells us that it explicitly does not apply to films or DVD rentals.
This makes は very powerful, and also makes it very easy to misuse: If you only want to state some information, you should not be using は. However, if you want to make sure that the context for some information is unmistakable, は is exactly the particle you want to use.
One very common use of this is in the form of social commentary, by pairing it with verbal て forms, followed by something that represents a negative commentary such as the word いけません, indicating that something "won't do", or the word 駄目, indicating something is bad:
literally: "(you) not coming over today will not do".
"(You) have to drop by today."
literally: "Eating it is no good."
"(You) may not eat this."
In these sentences, the negative repercussion is explicitly said to apply only in the situations marked by は. Also, because は is used, we know that they don't apply if whatever は is suffixed to doesn't apply.
Of course, sometimes it will feel like は isn't doing this strict disambiguation, such as in simple sentences like the following:
"Nice weather today, isn't it?"
"Actually, I'm horrible at Japanese."
In both sentences, the は looks perfectly innocent, but it's actually still doing the exact same thing. In the first sentence, the fact that 今日 has to be mentioned means that the situation of good weather is implicitly being contrasted to some previous, poor weather. Similarly, in the second sentence it seems like 実, 'truthfully' or 'actually', is fairly innocent, but the fact that it has been explicitly mentioned and marked with は means that the information that follows only applies in the context of 'true information'. Even when は sounds like it's just sitting in a sentence as a common courtesy, it never loses its additional connotation.
So in summary, we can characterise は as: [X]は[Y] → in the context of [X], [Y] applies, and outside the context of [X], [Y] does not apply. Put concisely, は not only tells us the applicable context, but also the inapplicable context.
Because of this, you will typically find は referred to as the 'context' particle (or 'topic' particle) in literature, but this is dangerous terminology, as it makes it really easy to forget that in addition to indicate context/topic, it also indicates the inverse at the same time. は never just marks applicable context, it always — always — also gives the inapplicable context simply by virtue of being used. If you don't want to also imply inapplicable context, use が — or を — instead.
(Almost) needless to say, this also means you never use は for things you're asking questions about. For instance, in the following example sentences, the first sentence is fine, and the second is very, very wrong:
"Who came (over)?"
"Who, as opposed to someone else, came (over)?"
This second sentence makes absolutely no sense, and you should never ever mark subjects of questions with は. Ever.
That said, you can use は in a question to disambiguate just fine, as long as it does not get used for the actual question subject:
"Who's recently been coming (over)?"
literally: "Lately [rather than during some other time frame], who has come (over)?"
I am quoting this passage directly from "All About Particles" by Naoko Chino:
Note: Wa has several usages, but its basic function is to set off a topic (e.g. of conversation) from the rest of the sentence, which talks about the topic. Technically wa does not indicate case (subject, object, etc.). However, in practical terms, it often (but not always) comes after the subject of the sentence. See also -te wa (#47) and to wa (#17)
- Indicates that information is being presented about something that is already known or that has been identified.
Asoko ni akai hon ga arimasu ne. Are wa kanji no hon desu.
Over there is a red book, right. It's a kanji book. / See the red book over there? That's a kanji book.
Ano daigaku wa, Yotsuya-eki no chikaku ni arimasu.
That university—it's near Yotsuya Station. / That university is near Yotsuya station.
- Indicates a topic, which is then identified or explained.
Ashita wa nichiyōbi desu.
As for tomorrow, it's Sunday. / Tomorrow is Sunday.
Kujira wa sakana de wa arimasen.
As for the whale, it is not a fish. / The whale is not a fish.
Note: if ga replaces wa in these sentences, the noun which it follows is no longer being presented as a topic but as the subject of the predicate (see ga, #2, I-2). The switch from topic (wa) to definite subject (ga) lays the stress on the latter. For example:
Asatte wa nichiyōbi desu ne.
Chigaimasu. Ashita ga nichiyōbi desu yo.
The day after tomorrow is Sunday, isn't it.
You're wrong there. Tomorrow is Sunday.
- In the construction N + wa N + ga, wa indicates a topic (the first noun) about which an aspect or quality (the second noun) is explained.
Zō wa hana ga nagai desu.
The elephant—its nose is long. / Elephants have long noses.
Takemoto-san wa seikaku ga yasashii desu.
As for Takemoto, her personality is gentle. / Takemoto has a gentle nature.
- Used to show contrast between two items or ideas, both of which are signified by wa.
Kanji wa muzukashii desu ga, Nihon-go no bunpō wa amari muzukashiku nai-n desu.
Kanji are difficult, but Japanese grammar is not very difficult. (笑) <- kakko-warai is mine
Hokkaidō no fuyu wa samui desu ga, Tōkyō wa atatakai desu.
The Hokkaido winter is cold, but [the] Tokyo [winter] is warm. / It's cold in Hokkaido in the winter, but warm in Tokyo.
Note: In some cases, only one item or idea is explicitly mentioned. For example, in the following sentence, the implication is that the person might go to a cheaper restaurant.
Takai kara, ano resutoran ni wa ikimasen.
Because it's expensive, I won't go to that restaurant. / I am not going to that restaurant because it's too expensive.
Note: In its contrastive function, wa comes after other particles (e.g., ni wa, de wa). Two important exceptions are when it replaces ga and o, as in the next example.
*Batā o kaimashita ka.
Māgarin wa kaimashitaga, batā wa kaimasen deshita.
Did you buy some butter?
I bought some margarine, but I didn't buy any butter. / I bought some margarine, but not any butter.
- In the forms V-te wa iru (first example below) and V-masu base folowed by wa and suru (second and third examples), wa indicates emphasis. See also -te wa (#47).
Konpyūtā o motte wa imasu ga, mada tsukatte (wa) imasen.
I own a computer [I do own a computer], but I haven't used it yet.
Ano hito o shitte wa imasu ga, amari hanashita koto wa arimasen.
I know him, but I haven't spoken to him much.
Ocha wa nomimashita ga, jikan ga nakatta no de shokuji wa shimasen deshita.
I had some tea, but since there wasn't much time, I didn't eat (have a meal).
I am somewhat unclear as to what you mean by "disambiguation" in that context. I would tend to call it "focus" rather than "disambiguation", as that conveys the meanings of both topic, emphasis, and contrast. Hope this helps.
Can particle は use cases be summarized by a single term disambiguation?
I don't think so. Even though there are many definitions of 助詞 は and it seems they are far from consistent, I think if you want the shortest definition is subject marker. But when I say it's a subject marker, I mean it as semantic subject marker and not syntactic one.
If you think of a construction like:
the syntactic subject (and the object) can't be determined without the context(usually this kind of utterance comes from a human point of view). And because they are semantic subjects, the sentence can be translated into either "As for me, I like cats." or "As for cats, I like them."
As for the topic/focus of conversation marker, it seems the が fits the bill. I think が is not only a semantic subject marker, it's also a semantic object marker. When you say:
This construction implies "out of all animals/things (I like cats)" and telling "it's cat" is the objective of conversation/sentence.