Where does component collide?

In physical chemistry a component is one of the smallest number of independent chemical substances needed to specify the makeup of every phase of a system at equilibrium. Gibbs fixed this quantity in his 1876 On the equilibrium of heterogeneous substances, where the count of components C enters the phase rule F = C - P + 2, which relates the degrees of freedom F of a system to its number of coexisting phases P. A single instance is a constituent counted as independent only after reactions and composition constraints are subtracted, so pure water counts as one component even though it contains hydrogen and oxygen. This referent is a bookkeeping count of independent substances in matter, not a blend of measured variables or a step in reasoning.[1]

Unit

One independent chemical substance in the phase-rule count C

Recovery means

Not applicable

Measured by

Found by counting distinct constituents and subtracting independent reactions and composition constraints

In statistics a principal component is a weighted blend of several measured variables, built so that it captures as much of their combined spread, or variance, as any single blend can. Pearson introduced the underlying geometry in his 1901 On lines and planes of closest fit to systems of points in space, finding the line or plane that sits closest to a cloud of data points, and Hotelling's 1933 Analysis of a complex of statistical variables into principal components gave the method its name and modern form. A single instance is one such blend, ranked by how much variance it accounts for, with the first component carrying the most. This referent is a direction through a data cloud, not a count of chemical substances or a mental operation.[2][3]

Unit

One weighted blend of variables, scaled by the variance it accounts for

Recovery means

Not applicable

Measured by

Computed as an eigenvector of the data's covariance or correlation matrix, ordered by eigenvalue

In the psychology of intelligence a component is an elementary mental process that acts on ideas or symbols, such as encoding a term, comparing two items, or drawing an inference. Sternberg set out this meaning in his 1977 book Intelligence, information processing, and analogical reasoning: The componential analysis of human abilities and stated it compactly in his 1980 Sketch of a componential subtheory of human intelligence, where reasoning is broken into timed processing steps whose speed and accuracy are estimated from how long people take on tasks. A single instance is one such information process, gauged by the time and error it adds to performance. This referent is a step in thinking, not a blend of variables or a count of chemical substances.[4][5]

Unit

One elementary information process, in time and error added to a task

Recovery means

Not applicable

Measured by

Estimated from reaction times and error rates on cognitive tasks, decomposed by mathematical modeling