energy density

Energy density is a measure of how much energy a material contains relative to its size or weight. It indicates how much useful energy is stored in a substance per unit volume (volume energy density) or per unit mass (mass energy density). For example, batteries with high energy density can store more energy in a smaller or lighter package, making them ideal for portable devices. Similarly, fuels with high energy density provide more power for a given amount of fuel. This concept helps compare different energy sources based on how efficiently they store and deliver energy.