真空(kong)(kong)，這(zhe)一術語譯自拉丁文vacuo，其(qi)意義是虛無。其(qi)實真空(kong)(kong)應(ying)理解為(wei)(wei)氣(qi)體較稀(xi)薄的(de)(de)空(kong)(kong)間。在指定的(de)(de)空(kong)(kong)間內(nei)，低(di)于一個(ge)大氣(qi)壓(ya)(ya)力的(de)(de)氣(qi)體狀態統稱為(wei)(wei)真空(kong)(kong)。真空(kong)(kong)狀態下氣(qi)體稀(xi)薄程(cheng)度(du)稱為(wei)(wei)真空(kong)(kong)度(du)（degreeofvacuum），通常(chang)用(yong)壓(ya)(ya)力值(zhi)表(biao)示。因此(ci)真空(kong)(kong)包(bao)(bao)裝實際上(shang)不是完全真空(kong)(kong)的(de)(de)，采用(yong)真空(kong)(kong)包(bao)(bao)裝技術包(bao)(bao)裝的(de)(de)食品容器內(nei)的(de)(de)真空(kong)(kong)度(du)通常(chang)在600-1333Pa。所以，又將真空(kong)(kong)包(bao)(bao)裝稱為(wei)(wei)減壓(ya)(ya)包(bao)(bao)裝或排氣(qi)包(bao)(bao)裝。