Numbers are almost always treated as adjectives, and often come before the noun. They may be used alone as substantive nouns, but as most are indeclinable, this tends to be ambiguous. Mille behaves differently; in the plural, as milia , the noun being counted must be in the genitive plural. For example, "two thousand soldiers" would be " duo milia militum " (literally, "two thousands of soldiers). Thus a mile is mille passūs (literally, "a thousand paces"), but two miles is duo milia passuum (literally, "two thousands of paces").