The "contents" are the item inside a bottle or container.
A cravat is worn inside a shirt collar.
a Ziploc bag because it stores things
The baby bottle
Any item has berkelium inside.
The item that a baby is typically baptized in is called a baptismal font or baptismal basin. It is often a container filled with water that is used for the baptism ceremony.
Apothecary jars are now a popular home decor item: http://www.ehow.com/how_4999162_enhance-bathroom-decor-apothecary-jars.html Sheryl
The analogy is "hat is to head as lid is to container." In both cases, the first item (hat or lid) is used to cover or protect the second item (head or container).
plastic toy container
You can have various items with capacity of 1 liter. You can have a jug or bottle with 1 liter capacity.
A pumice stone. An empty bottle with its top on.
An item in a set is called an element.An item in a set is called an element.
The shape of an item can be patented. It is called a design patent. The most famous is probably the shape of the Coca Cola bottle.