"Light" enough to be air-lifted. As opposed to so "heavy" it needs to be sealifted. There is no "medium" except in Shinseki's fever dreams. The definition of a "light infantry division" is so precise it requires several binders to properly define, though, so I'm not sure where you're getting the idea that "military germs" are "vague and straightforward" (somehow) TBH. There is an actual tonnage/mass that goes into defining the distinction, which is a function of airlifter capacity, mission range, turnaround times, airport throughput, and cycle periods; but since that tonnage varies it's usually stuck on weird things that serve as hypothetical ballparks, like "airlift this brigade 4,500 miles from Fort Drum to Bosnia" or whatever.
Manokan Republic wrote:what the hell does "operation" mean
When the genius level IQ can crack the mystery of "semantics" and "context" you can answer this question for yourself.