This is an introductory text on the concepts of measurement and measurement uncertainty. It is an expanded version of material found on the online training website LearningMeasure.com (http://www.learningmeasure.com) and can be used as a handy reference for the courses. It is meant for those interested in measurement and metrology. The concepts and techniques described are applicable to all forms of measurement and test, but in particular in the area of metrology, the science of measurement. This is a first in a series of texts on measurement and metrology. Included in the purchase price is a three month subscription to LearningMeasure.com, see chapter 14 for details.