A capital delta before an H, denoting heat absorbed or released.
Also known as: Delta H, Triangle before an H
ΔH is the heat change of a reaction, and its sign is the whole message: negative means heat released. Getting the sign backwards is the commonest error in thermochemistry, because the convention is stated from the system's point of view.
Denotes the change in enthalpy over a reaction, which at constant pressure is the heat absorbed or released.
Contexts: Mathematics, Laboratory
Carries its meaning in its sign: negative for an exothermic reaction releasing heat, positive for an endothermic one absorbing it — stated from the system's point of view rather than the observer's.
Contexts: Mathematics, Laboratory
Uses the capital Greek delta generically for 'change in', a convention applied to any quantity rather than specific to enthalpy.
Contexts: Mathematics, Laboratory
A capital Greek delta drawn as a plain triangle, immediately followed by an italic capital H, often with a superscript symbol for standard conditions.
The delta is the generic 'change in' operator applied to enthalpy.