Abstraction

The intentional omission or simplification of details of a phenomenon, which allows the design of a manageable conceptual, mathematical or computational model. A representation that focuses on details relevant to the question of interest.

Activator

A molecule or entity that increases the capacity of a process.

Ad hoc model

A mathematical model that is constructed for a specific purpose and without adhering to prescribed model design rules, as opposed to a canonical model.

Adaptive system

A computational or natural system that adjusts its own internal settings to improve its tolerance toward changes in inputs or in its environment.

Affinity

An attractive force between entities. In the case of atoms or molecules, affinity may lead to a chemical reaction.

Agent-based modeling

A simulation method for discrete models, in which each component is an agent whose actions are determined by specific rules. Agents may be humans, animals, cells, molecules or even single atoms.

Algorithm

A sequence of operations or commands constituting a numerical procedure or computer code.

Alkaline

A chemical or solution that is basic, with a pH greater than 7.

Alternative splicing

A mechanism allowing peptides that were transcribed from the same gene and translated from the same mRNA to be combined into different proteins.

Amino acid

The molecular building blocks of proteins. While about 500 amino acids are known, only 22 are used in proteins, and only 20 are directly represented by the genetic code.

Antagonism

A situation where two components act against each other or diminish each other's effect. Antonym of synergism.

Antibody

One of many key proteins of the immune system that sense and neutralize foreign molecules and organisms in the blood. Antibodies are very specific in their binding to non-self entities. Also called an immunoglobulin.

Apoptosis

The technical term for programmed cell death. A complex process in which a cell is genetically programmed to die under certain conditions.

Approximation

The replacement of a (complicated) function with another (simpler) function that retains some, but not all, important features. Usually, the approximation and the approximated function have the same value and the same slope(s) at one point that can be selected as most important for representing a particular situation.