Medium-dark sits between medium and dark within a seller's roast range. CoffeeBox describes a shift toward caramel, dark chocolate, toasted and smoky impressions, with bitterness becoming more noticeable. These terms describe an intended sensory style rather than a chemical rule that all acids have disappeared or changed directly into caramel. The actual balance depends on the coffee and its roast development.
The guide draws examples from Brazil, Guatemala and Honduras and discusses pairing the resulting coffee with milk. Such combinations are possibilities rather than automatic outcomes of the origin or roast label. A darker-looking bean also does not prove that the original coffee was inexpensive, defective or unable to support a lighter roast. Quality and roast preference are separate questions.
When comparing medium-dark offerings, look for a clear lot or blend description and the roaster's intended use. Taste with the preparation you normally drink, noting whether roast character supports or overwhelms the other impressions you value. Record milk and dilution amounts if they are part of the drink. Store beans as directed in a suitable closed package; visible oil alone cannot establish a universal number of days before a coffee becomes unacceptable.

The conversation
A good question can make a better brew.