Such a nanopublication defines a new class. Classes represent sets of concrete or abstract things, and are by convention named with singular nouns (or noun phrases) like 'human', 'cardiovascular disease', or 'approach'.
If the term you want to define does not refer to a set of things but a single instance, such as the planet Mars or Marie Curie, define them with the template for individuals instead.
This variant of the 'Defining a new class' template additionally allows for linking the class to the FAIR principles it enables (for FAIR-Enabling Resources) or supports (for other FAIR Supporting Resources).