Kilo — NATO Phonetic Alphabet for K

Kilogram, kilometer, kilobyte — and now K. Kilo is the rare NATO phonetic alphabet entry drawn directly from a globally standardized unit prefix rather than a name or an invented-sounding word, already familiar in something close to its English form across most of the world.

Hoisted alone as a maritime signal flag, Kilo simply means "I wish to communicate with you" — a general opening signal rather than a description of a specific emergency or condition.

The word has also lent its name well outside spelling and flags: NATO reporting names for Soviet and Russian submarine classes are drawn directly from this same 26-word alphabet, and the Kilo-class submarine, still in active service in several navies today, is named after this exact letter. Because the word was already tied to a fixed, internationally agreed unit of measurement, its meaning was effectively locked in decades before ICAO ever attached it to a letter.