Some languages have no definite or indefinite article, for example, I think, Polish. So the Polish word kot could mean "a cat" or "the cat". So in a glossed example, and not knowing the context, how do we represent this in the translation? I guess it could be 'a/the cat', or could you pick one form - definite or indefinite - and stick with that form throughout an essay etc.?
As was said in the comments, just selecting one arbitrarily and sticking to it is probably a bad idea as this could be confusing. Your best options are probably to either:
Provide the necessary context so as to resolve the definiteness of what is being referred to.
Use 'a/the' in the translation line. An example of this can be found in the WALS Online entry for definite articles in the example from the Cherokee language.
It probably depends on the purpose of your example. If it is to point out that the language does not possess definite or indefinite articles (as in the Cherokee examples), then the second option would be the way to go, otherwise it's up to you I guess.
If you want to show that you mean particularly this cat you can say ten/tamten kot (this/that cat). Otherwise you don't need to add any article.
This information (definite/indefinite article) is not important, exactly like in English there is no gender for any noun - just a cat/mouse/animal, not ten(kot)/ ta(mysz)/to (zwierzę) or like in German der/die/das...