numerus

Numerus, numeri, m., second declension. Beyond plain arithmetic it means a group counted as a body, which produces the very common idiom in numero habere, "to count among", and its harsher cousin in hostium numero habere, "to treat as an enemy".

The second sense is metrical. In verse and in rhetorical prose numerus is rhythm, the count of the feet, which is why Cicero discusses numerus when he means the cadence of a sentence and why English number once meant a line of verse. The plural can also mean the parts that make a whole complete, giving omnibus numeris absolutus, "perfect in every respect". From it come number, numeral, enumerate and French nombre.