Yes, capital goods and consumer goods aren't the only ways products (as in goods & services) are classified.
Free, Private, and Public
These questions are not to be assessed on a linear scale -- that is to say, an underground train is not of a rivalrous nature if it isn't crowded.
Some examples include:
- street lights are inexclusive and non-rivalrous;
- (most) British motorways are inexclusive and non-rivalrous to a point;
- sunlight is inexclusive and non-rivalrous.
These properties are key to considering whether a product is public, quasi-public, private, or free.
Public goods often lead to the free-rider problem: due to their inexclusivity and unrivalrousness, those who use it won't be compelled and often won't pay, leading to a lack of incentive to provide, and thus lack of provision, for such goods.
The free-rider problem can also be classified as an example of market failure.
Examples of truly public goods are rare: count national defence, street lighting, flood control, and lighthouses.
Quasi-public goods are generally easier to find examples for:
- Inexclusive, rivalrous goods like the M25 or underground trains;
- Exclusive, non-rivalrous goods like the M6 Toll or Netflix.
A grand majority of things can be considered public goods: food, clothing, computers, etc.
Merit, Demerit, and Externalities
Merit and demerit goods exist in a separate category to public and private goods.
That is to say, the M25 is, simultaneously, a quasi-public and demerit good (congestion, eh?).
Normal, Inferior, Subsitutes, and Complements
The distinction between normal and inferior goods is as vague as that between merit, demerit, public, and private goods. Please also consider other factors as well.
The price of substitutes and demand for the currently-considered goods move inversely,
the price of complements and demand for the currently-considered goods move directly.
