* 2.0 engine: This refers to the engine's displacement, specifically 2.0 liters. Displacement is the total volume of all the cylinders in an engine. A larger displacement generally means more power, but also more fuel consumption. A 2.0L engine could be any type of engine (e.g., inline-4, V6, etc.) and have various valve train designs.
* DOHC engine: This refers to the valve train design, specifically "Double Overhead Camshaft." This means the engine has two camshafts located in the cylinder head (overhead), one for the intake valves and one for the exhaust valves. DOHC designs generally allow for more precise control over valve timing and lift, leading to better performance and efficiency compared to single overhead camshaft (SOHC) engines.
In short: They are not mutually exclusive. You could have a 2.0L DOHC engine (very common), or a 2.0L SOHC engine, or a 3.0L DOHC engine, etc. The "2.0" describes the size, while "DOHC" describes a specific feature of the internal design.
