Count nouns are enumerable and can form plurals: bikes, buses, oxen, persons, ideas, etc. Mass nouns are innumerable, often abstract, and do not have plurals: bravery, power, physics, wood, etc. Mass nouns are easy to identify since they cannot be preceded with a or an. A few nouns, however, can be both count and mass nouns, though these are few and far between. The baby has five hairs (count noun), She has too much hair (mass noun); Two coffees please (count noun), I’ll have a cup of coffee (mass noun).