In English, we use the same verb for existence and linking. We can say “is/am/are” to mean exist or to mean has the quality of being something else. For example:
There are books.
Those books are bad.
In classical Tibetan, however, existence and linking are different verbs. ཡིན་ is the basic linking verb. ཡོད་ is the basic verb of existence.
དེབ་ཡོད།
BOOKS[S] EXIST
དེབ་དེ་སྡུག་ཅག་ཡིན།
BOOK THAT BAD IS.
Notice how the sentence that says “book[s] exist” does not say anything about how many books exist. Could be one. Could be a billion. We have no idea.
Also notice the use of དེ་ in the second sentence. Without that article, we really have not idea if we are talking about a specific book, the set of all books, or what. Tibetan doesn't use definite and indefinite articles the way English does, such as “the” or “an.” But this type of usage of a “this/that/those” (an adjective) is common. Tibetan will commonly say things such as the following to specify plurality and ensure the reader understands that the writer is speaking about a specific book or set of book.
དེབ་དིར་
This book.
དེབ་དེ་
That book.
དེབ་དེ་ཚོ་
Those books.
དེབ་རྣམས་
Books (explicitly plural).
དེབ་གསུམ་
[the] three books
Now, to further complicate things, Tibetan uses the same verb for existence and possession, unlike English which uses different verbs for existence (am/are/is) and possession (have).
དེབ་ཡོད།
BOOK[S] EXIST
There is [a] book. There are book[s].
ང་ལ་དེབ་ཡོད།
ME-FOR BOOK[S ] EXIST
I have [a] book. I have book[s].
[very literally] For me, book[s] exist.
ང་ལ་དེབ་གཅིག་ཡོད།
I have one book.
[very literally] For me, one book exists.
Possession, which classified as a type of specialized verb in the Wilson system, does not translate very well literally in English. In English, we should say, “I have a book." The Tibetan sentence above does not actually say “a” book, but specifies some undefined, non-zero number of books. Further, more literally, it might be read as saying, “[a/the/many] book[s] exist for me.”
Ultimately, the challenge is that classical Tibetan, which is derived largely from Sanskrit, signifies meaning in a way that is simply structurally different than English. When Tibetan say ང་ལ་དེབ་ཡོད།, what they mean is “I have [some number of] book[s].” What they would more likely say is something like : ང་ལ་དེབ་གཅིག་ཡོད། Or: I have one book. However, they are not saying for me one book exists, which is how an achingly literal translation might read. The point here is that Tibetans aren't even thinking for me one book exists, either. They are thinking I have a book. This is just signified in a different manner than in English.
This tension between how things are signified and the signified meaning will come up repeatedly in attempting to translate classical Tibetan. In some cases, the difference is important and a more literal translation may be warranted. For example, it is important to understand explicitly how plurality is handled and the lack of explicit plurality in nouns. However, in other cases, such as in the case above, it is not. Translating ང་ལ་དེབ་གཅིག་ཡོད། as “for me one books exists” would be silly.