Clamshell Heat Press | Hotronix Auto Open Clam | Stahls’

Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams have two shells of equal size connected by two adductor muscles and have a powerful burrowing foot. They live in both freshwater and marine environments; in salt water they prefer to burrow down into the mud and the turbidity of the water required varies with species and location; the greatest diversity of these is in North America.

Clams in the culinary sense do not live attached to a substrate (whereas oysters and mussels do) and do not live near the bottom (whereas scallops do). In culinary usage, clams are commonly eaten marine bivalves, as in clam digging and the resulting soup, clam chowder. Many edible clams such as palourde clams are ovoid or triangular; however razor clams have an elongated parallel-sided shell, suggesting an old-fashioned straight razor.

Some clams have life cycles of only one year, whilst at least one has been aged to more than 500 years. All clams have two calcareous shells or valves joined near a hinge with a flexible ligament and all are filter feeders.

Clamshell may denote anything resembling the bivalve shell of a clam:

• Scoop stretcher, another name for this patient transport device
• Clamshell design, a form factor used for electronic devices, also known as a "flip" or "flip phone".
• Clamshell (container), a design used for storage and food packaging, usually made of plastic or paperboard.
• Clamshell case, a type of box for storing paper items in archives (may also refer to either of the two uses above - electronics or packaging)
• Gallet Clamshell, the world's first water resistant chronograph wristwatch
• Bucket (machine part)#Clamshell bucket, or clamshell bucket
• Clamshell Alliance, an anti-nuclear organization
• Clamshell Falls, a waterfall in Australia

In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by modes other than thermodynamic work and transfer of matter. Such modes are microscopic, mainly thermal conduction, radiation, and friction, as distinct from the macroscopic modes, thermodynamic work and transfer of matter. For a closed system (transfer of matter excluded), the heat involved in a process is the difference in internal energy between the final and initial states of a system, and subtracting the work done in the process. For a closed system, this is the formulation of the first law of thermodynamics.

Calorimetry is measurement of quantity of energy transferred as heat by its effect on the states of interacting bodies, for example, by the amount of ice melted or by change in temperature of a body.

In the International System of Units (SI), the unit of measurement for heat, as a form of energy, is the joule (J).

With various other meanings, the word 'heat' is also used in engineering, and it occurs also in ordinary language, but such are not the topic of the present article.