Italian is an instance of a language.
IE and FireFox are instances of internet browsers.
Technical stuff follows:
There is a distinction between subset and member (or instance) but sometimes they overlap. For a set (a collection of things) one can have a subset (a subcollection). A given set can have many members -inside- it. A subset is of the same kind as the superset. A member can be any kind. A subset of size exactly 1 is usually thought of as a member or instance (because it sounds weird informally to call a subset of size 1 'a subset', i.e. "Italian is a subset of Romance languages", though technically correct sounds goofy when you think of Italian as a single language (linguistically one can think of Italian as the set of only partially mutually intelligible dialects spoken by people on the Italian peninsula).
So if you start with the set of all languages, you can then have the subset of European languages, and a subset of that the Romance languages and then the subset (or better, the instance) Italian.
The subset relation forms a hierarchy (formally a partial order) described by 'is-a'. A circle is an ellipse is a curve.
A hypernym is the word for the concept that is a parent/ancestor/predecessor/superset/superclass of the hyponym.
A hyponym is the word for the concept that is a child/descendant/successor/subset/subclass of the hyponym.
As to member, because membership is not usually thought of as a transitive relation, it doesn't really have all these successor/predecessor terms.