Different languages do things differently, and a rarely can a word in one language translate a word from another language in all of uses (and only there). Sometimes it can be difficult to see what ties together all the uses of a word, even when speakers insist that they are not just homonyms.
Consider the word lə in Lefa, which is often translated 'that" in English.
In English, “that” has several uses. It is a demonstrative, as in “that book”, where it relates to “those”, as well as “this” and “these”. It is a relative pronoun, as in “the man that I saw”, where it relates to “who / whom” at least in some cases (for people).
But it is also a “complementizer”. This means it introduces a clause as the object of a verb. Examples of this would be “I saw that …”, “I know that …”, “I hope that …”, etc. It is this last use that is covered by lə in Lefa. There are separate words for demonstratives and relative pronouns, all of which change according to the “gender” of the noun modified (In what follows, it is important to not interpret lə THAT as a demonstrative or relative pronoun).
Many of the uses of lə are common for complementizers – including all the uses listed above (with verbs for see, know, want, etc.). As in English, it can be used for some adjectives:
It would be good THAT ...
In addition, lə can be used for purpose or reason clauses (the form of the verb in the clause distinguishes between these meanings):
She left THAT she would look for wood – purpose.
Turtle started THAT he liked to walk alone – reason
Although this use is a bit strange in English, it is common in other languages. Another similar use that is seen elsewhere is lə used for “such that”
If you are a man THAT you are married – “a man such that you are married”
One use that clearly comes from these uses but is quite strange in English is for introducing speech without a verb:
He THAT x = “He said that x” or "He said, 'x' "
This is actually quite common in some African languages, and even other languages around the world. A further extension of this happens when lə is used after another verb and adds the idea of speaking:
You just take it THAT it is mine = “saying it is mine“ (not reason because we have “mine“ and not “yours“)
Besides these uses, there are some that seem quite strange for English speakers, but still can make sense. Lə is often required in the context of names:
My name is THAT Kendall (remember, not a demonstrative as it would be in English)
They call them THAT bags.
the village of THAT Zok (again, not a demonstrative)
In this last case, the use of lə THAT means that you are giving the name of the village, if you just said “the village of Zok” it would be where a man named Zok lives (like “Zok’s village” in English).
These “naming” uses can be seen as relating to the “speech alone” use, almost like quotation marks.
One other use in this area is in description. As with many African languages, many verbal description words (“adverbs”) are related to onomatopoeia and act somewhat like “bang!” or “woosh!” in English. In this context, lə is required. Using something related to “saying” for this kind of descriptor is not at all uncommon in languages (it happens in Japanese, for example).
You can't pick it up THAT (grunt) – pick it up easily, suddenly, with a heave
I speak Lefa THAT little.
Another interesting use, clearly related to its use as a complementizer, is after the verb "to be" and a following clause with the same subject, used to mean "can":
I am THAT I come = I can come.
For all these uses, although some are strange for English, and although their number in one and the same language might be a bit unusual, none are totally unexpected for a complementizer. The following uses, however, are quite surprising, even cross-linguistically.
These uses are at the end of a clause, or nearly, with just a location sometimes following.
Lə can be used in the phrase “Here I am”
This me THAT here.
In this case lə is optional, and adds some type of emphasis.
In another emphatic statement it is required.
John he came THAT (bolded he is a different form that indicates emphasis)
In still another case, it is required and seems to be the only mark of the emphasis:
I’m waiting for you THAT here.
Finally, lə is also required when using a “both / and” listing of two or more items.
I saw THAT both Kendall and Renee
these three towns THAT both Deuk and Ngoro and Ngambe-Tikar.
So, how can we group these uses? Several seem connected as that of a complementizer or extensions from there. These would be the first ones discussed, as well as the speaking and naming uses. Several are linked in emphasis. And then there is the listing use. But I don’t really see the connections between these three groups of uses.
If you still haven't gotten enough and want to explore this more in depth, see a preliminary version of my paper here.