count
Countexact by definition
A count is a plain number of discrete things: bolts, people, samples, pump starts. It carries no physical dimension and no unit in the ordinary sense, which is why its conversion factor is one and why there is nothing to convert it to. Counts are exact by their nature, since a whole number of objects has no measurement uncertainty of its own.
Watch out: A count is a whole number of separate items, while a dimensionless ratio is a pure number formed by dividing two like quantities and may take any value including fractions and a percent form. Twelve bolts is a count; a 0.12 efficiency or 12 percent is a ratio. The two are both unitless but they are not the same kind of number, and averaging counts produces a ratio rather than a count.
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