Each

One individual item — the smallest unit a thing can be ordered, delivered or counted in.

Why it matters operationally

It is the base unit everything else converts to. A crew chief counting on a dock counts eaches; a buyer negotiating counts cases or pallets. If the conversion between the two is not written down, the two numbers will disagree and someone will assume the count is wrong rather than the unit.

How Roadmap handles it

Where an item has a case pack, the conversion is part of the catalog record rather than something a person applies in their head.