True score =  a theory that maintains that an observed score is the sum of two components true ability (or the true level) of the respondent and random error.

Random error = a component or part of the value of a measure that varies entirely by chance. Random error adds noise to a measure and obscures the true value.

Systematic error = a component of an observed score that consistently affects the responses in the distribution.

Cronbach’s coefficient alpha is an internal consistency estimate of scale reliability that is mathematically equivalent to all possible split half estimates of reliability.

Cronbach's alpha is a measure of internal consistency, that is, how closely related a set of items are as a group. It is considered to be a measure of scale reliability. A “high” value for alpha does not imply that the measure is unidimensional.

The approximate truth of falsity of assertions regarding the intended consequences of test interpretation and use.
Consequential validity bring attention to the fact that there are personal and social consequences of test scores.