What is defined as a point of measurement in a titration?

The end point is defined as a critical moment in a titration where the reaction is complete, indicated by a distinct change in a measurable property, often signaled by a color change if an indicator is used. This point represents the stage where the amount of titrant added is stoichiometrically equivalent to the analyte in the solution. Understanding the end point is crucial for accurate determination of concentration in quantitative analysis, as it marks the precise moment at which the titration has effectively reached its desired level.

The other choices relate to different aspects of the titration process but do not define a point of measurement. The start line could refer to the initial volume of the titrant or the baseline measurement but does not indicate a completion. The titrator is the device or substance used to perform the titration, and the calibrator usually refers to equipment or methods used to ensure measurement accuracy, rather than a specific point in the titration process.