But where store-of-value considerations are important, as they are in richer, more civilized societies, the medium of exchange must be a durable commodity, usually a metal.

但是，当价值储存变得相当重要时，在那些人民更富裕，更文明的社会里，交换的中介必须是种更为耐用的物品，通常金属会被选中。

youdao

The brunt of the blast is projected straight ahead, forcing a powerful spike of metal, usually copper, into and through the armour.

爆炸的正面直接投射在装甲上，迫使强大的金属尖刺（通常是铜）穿透装甲。

youdao

Hut is a small house or shelter, usually made of wood or metal and in the past was a temporary structure for sheltering troops.

棚屋是一间小房子或住所，通常用木头或金属建造而成，过去用作避难人群的临时建筑物。

youdao

The origins of the pencil date to the ancient Romans, who used to write with a device known as a stylus--a metal stick, usually lead, which was used to scratch words onto papyrus.

FORBES: No. 4 The Pencil

Stronger steel usually requires tradeoffs on other properties, like ductility, a metal's ability to be shaped into forms like sheets and wires.

FORBES: Steely Dan