**Abstract**

Any use of both ionizing radiation and nuclear technologies requires ensuring appropriate safety and security of persons as well as the adequate protection of the environment. This is why the applications and handling of sources of ionizing radiation should be in line with the relevant national and international standards containing appropriate safety and security requirements and recommendations. In order to understand and follow these standards, it is necessary to assess the related radiation risks, which should be quantified by using specific dosimetry and radiation protection quantities and units. The chapter introduces and discusses these quantities and units aimed at the evaluation of the biological harms attributed to both stochastic and deterministic effects. The correct use and interpretation of radiation quantities are important to follow relevant regulations and to communicate radiation risks to workers and the public. The chapter takes into account the latest situation in the field, relying on the recent position of relevant international expert bodies.

**Keywords:** radiation, protection, use of radiation, radiation technologies, international standards
