Premise: The AK-47 ( [ Автомат Калашникова , translit = Avtomat Kalashnikova , lit = Kalashnikov 's Automatic Rifle ] ) is a selective-fire ( semi-automatic and automatic ) , gas-operated 7.62 × 39 mm assault rifle , developed in the Soviet Union by Mikhail Kalashnikov . It is the originating firearm of the Kalashnikov rifle ( or `` AK '' ) family . Even after almost seven decades , the model and its variants remain the most popular and widely used assault rifles in the world because of their substantial reliability under harsh conditions , low production costs compared to contemporary Western weapons , availability in virtually every geographic region and ease of use . As of 2004 , `` Of the estimated 500 million firearms worldwide , approximately 100 million belong to the Kalashnikov family , three-quarters of which are AK-47s '' .
Hypothesis: AK-47 is a knife.
Label: ENTAILMENT