n., pl. -ties.

1. The state of being active.
2. Energetic action or movement; liveliness.
3. 1. A specified pursuit in which a person partakes.
   2. An educational process or procedure intended to stimulate learning through actual experience.
4. The intensity of a radioactive source.
5. The ability to take part in a chemical reaction.
6. A physiological process: respiratory activity.

The activity of a substance is a thermodynamic property that is related to the chemical potential of that substance. Activities are closely related to measures of concentration, such as partial pressures and mole fractions. The conditions that hold in chemical reaction equilibrium and in phase equilibrium can be expressed in terms of activities of the species involved.

The activity a_i of chemical species i in a phase (a homogeneous portion) of a thermodynamic system is defined by Eq. (1), where
1.
μ_i is the chemical potential of i in that phase, μ°_i is the chemical potential of i in its standard state, R is the gas constant, and T is the absolute temperature. Equation (1) shows that the activity a_i depends on the choice of standard state for species i. Since μ_i is an intensive quantity that depends on the temperature, pressure, and composition of the phase, a_i is an intensive function of these variables. a_i is dimensionless. When μ_i= μ_i°, then a_i = 1. The degree of departure of a_i from 1 measures the degree of departure of the chemical potential from its standard-state value. The chemical potential is defined by μ_i ≡ ∂G/∂n_i, where G is the Gibbs energy of the phase, n_i is the number of moles of substance i in the phase, and the partial derivative is taken at constant temperature, pressure, and amounts of all substances except i. See also Free energy.

From Eq. (1), it follows that μ_i is given by Eq. (2).
2.
The chemical potentials μ_i are key thermodynamic quantities of a phase, since all thermodynamic properties of the phase can be found if the chemical potentials in the phase are known as functions of temperature, pressure, and composition. Activities are more convenient to work with than chemical potentials, because the chemical potential of a substance in a phase goes to minus infinity as the amount of that substance in the phase goes to zero; also, one can determine only a value of μ_i relative to its value in some other state, whereas one can determine the actual value of each a_i.

---

In Program Evaluation and Review Technique (PERT), the action that consumes time or resources. Activities are represented by arrows in a PERT network.

noun

Energetic physical action: exercise, exertion. See action/inaction.

n

Definition: special interest or pursuit
Antonyms: hate

n

Definition: state of being active
Antonyms: idleness, immobility, inactivity, indolence, inertia, laziness, sluggishness

---

In CPM terminology, a task or item of work that must be performed in order to complete a project.

---

The quality or process of releasing energy or of accomplishing an effect.

• displacement a. — an instinctive behavior pattern, exhibited out of context and believed to be a means of relieving tension in the animal. Usually performed when the animal is in a state of high arousal or when it is frustrated in the performance of some instinctive activity. Seen as sexual mounting, digging, tail chasing, or excessive grooming in cats.
• economic a. — a method of producing a specific product, e.g. fine wool, white veal.
• enzyme a. — the catalytic effect exerted by an enzyme, expressed as units per milligram of enzyme (specific activity) or molecules of substrate transformed per minute per molecule of enzyme (molecular activity).
• a. gross income — the total value of production, rather than the income, for a particular activity.
• a. gross margin — the gross income of an activity less its variable costs.
• intermediate a. — production of a commodity which is not sold but is used as an input to some other enterprise, e.g. crop used on the farm as stock feed.
• optical a. — the ability of a chemical compound to rotate the plane of polarization of plane-polarized light.

(DOD) 1. A unit, organization, or installation performing a function or mission, e.g., reception center, redistribution center, naval station, naval shipyard. 2. A function, mission, action, or collection of actions. Also called ACT. See also establishment.

IN BRIEF: Motion; the condition of being lively or busy.

There is always a lot of activity during recess.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - aktivitet, virksomhed

Nederlands (Dutch)
activiteit, tekenen van leven, werking, radioactiviteit professionele werkzaamheden

Français (French)
n. - activité, occupation, mouvement (d'une ville, d'un port)

Deutsch (German)
n. - Tätigkeit, Aktivität, Beschäftigung, Betriebsamkeit, Geschäftigkeit

Ελληνική (Greek)
n. - δραστηριότητα, ενεργητικότητα, απασχόληση, ενασχόληση, εκδήλωση

Italiano (Italian)
occupazione, attività

idioms:

• professional activity    attività professionale

Português (Portuguese)
n. - atividade (f), ação (f), presteza (f), vivacidade (f), energia (f)

idioms:

• professional activity    atividade profissional

Русский (Russian)
деятельность, профессия, занятия

idioms:

• professional activity    профессиональная деятельность

Español (Spanish)
n. - actividad, ocupación, quehacer, trabajo, diligencia

Svenska (Swedish)
n. - verksamhet, aktivitet

中文（简体） (Chinese (Simplified))
活动, 行动, 活动力, 活力

中文（繁體） (Chinese (Traditional))
n. - 活動, 行動, 活動力, 活力

한국어 (Korean)
n. - 활발, 활동, 호경기

日本語 (Japanese)
n. - 活動, 活気, 行事, 活発

العربيه (Arabic)
‏(الاسم) فعاليه, نشاط‏

עברית (Hebrew)
n. - ‮פעילות, פעלתנות‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.

activity cube	fisher price activity walker
Lego Activity Table	franklin activity center