Universe of Discourse.
There generally is when one talks or writes - tacitly - supposed to be something one talks about, that may be "the real world", but need not be so at all, in at least four distinct ways:
1. One may be speaking about the real world, but not as it is yet known: In the future, or perhaps in an unknown past.
2. One may be speaking about the real world, but in a constrained way, such as: what can be shown by good physical experiments, or in some limited field ("in the economical world").
3. One may be speaking about some domain one knows not to be real, such as the Greek gods of antiquity, the characters in Shakespeare's plays.
4. One may be speaking about some domain about which one knows that there is much one does not know: One may have explicit hypothetical entities, or doubtful facts (such as may be on maps one does not trust or knows to be partially faulty).
Note that in any of these cases, one still can be using the words "true" and "false", and then by reference to the domain one supposes oneself to talk or write about.