Ounces are an imperial unit. They are a bit confusing as they can be a volume unit or a mass unit. The metric equivalent would be gram or millilitre.
About 30 gram = 1 oz
About 30 mL = 1 fluid oz
Ounces and mg.
Capacity can be measured using both the metric system and customary units. In the metric system, capacity is typically measured in liters or milliliters, while in the customary system, it is measured in ounces, cups, pints, quarts, and gallons.
It is a customary unit.
The opposing systems are imperial and metric, not customary. But, meters are metric.
The pound is NOT a metric unit.
It is customary.
It can be more or less. An once (customary) is bigger than a gram (metric) but a pound (customary) is smaller than a kilogram (metric).
Metric.
Metric.
Metric
customary
It is a customary unit.