A recommendation letter or letter of recommendation, also known as a letter of reference, reference letter or simply reference, is a document in which the writer assesses the qualities, characteristics, and capabilities of the person being recommended in terms of that individual's ability to perform a particular task or function.
This article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.his article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.
A radioactive isotope is a form of an element that is unstable and eventually decays into a different element. For example, most Carbon has 6 protons and 6 neutrons, and is st â¦ able. radioactive isotope is a form of an element that is unstable and eventually decays into a different element. For example, most Carbon has 6 protons and 6 neutrons, and is st â¦ able.