One who or that traces.

追踪者(物)。

One whose business is locating lost persons, packages, or property.

遗失物(人)追查员。

Inquiry sent out for the recovery of lost letters, packages, etc.

遗失物查询。

Chemical added to ammunition to cause it to trail smoke and fire when fired, for the purpose of making its path visible.

【军】曳光弹；发烟弹(=tracer bullet)。

Substance, generally radioactive, whose presence or path can be traced in a biological chemical, or physical system.

示踪物(通常是一种放射性物质，在生化及物理系统中，其存在与行动路线能够追踪得出)。