An entity is a kind of abstract species that can be used in formation reactions.

Each entity gets the following variables:

<entity>.logact (log activity for aqueous species, intensity for other entities)

<entity>.con    (entity concentration in its home phase)

and furthermore for each system phase:

<entity>.<phase>     (cumulative mass balance for primary entities, contains mass of all derived entities in all child phases in units of indicated phase)

<entity>.<phase>.con (individual entity concentration in units of given phase)

Example:

@entity(e-, diss,0)

Derived forms of entities are: species, gases, minerals, sites, solid solutions, electrostatic planes etc.