Metrology, every bit defined per International Organization of Legal Metrology (OIML) [http://www.oiml.org/] in its 2000 publication International Vocabulary of Terms in Legal Metrology [http://www.oiml.org/publications/V/V001-ef00.pdf], is the “Science of Measurement." Legal metrology is further defined in this same international standard as: "part of metrology on to activities which symptom from either statutory requirements & concern measurement, units of measurement, measuring instruments & methods of measurement and which are then performed by competent bodies." [ibid] The International Bureau of Weights and Measures (BIPM) [http://www.bipm.fr/] further defines metrology as "...a science of mensuration, embracement each experimental and theoretical determinations at any level of uncertainty in any field of Science and Technology." [http://www.bipm.org/en/bipm/metrology/]

Introduction
Historical development

Historically measures of space are defined as discrete units of length, area, and volume. Measures of time are defined as a length of time for which a phenomena may be observed. Time is thought of both as an ongoing and continuing process and as having a period or duration for an event and so may be additionally described as cyclical, sequential, periodic or a singularity. Measures of other physical properties such as weight are defined first as physical properties of the space time continuum and then given additional descriptors such as mass and energy.

Mechanisms of metrology

One small subset of this study has to do with standards of measure. A small subset of that area of study is the definition of standards and the scientific methodology of ensuring that standards of measure meet specified degrees of accuracy and precision. In the United States, the master reference Standards are maintained through the National Institute of Standards and Technology (NIST). By convention, a Standard is ten times more accurate and precise than the measurement being tested.

The process of comparison against a Standard, and making any necessary adjustments, is commonly called calibration. Detailed records are maintained for each item that is calibrated to ensure "traceability", and that the item met clearly identified specifications for both accuracy and precision in all its operating parameters.

Collaboration between NIST and its counterparts in other countries and with the BIPM ensures the highest achievable Standards.