The Sun is losing mass from the emission of electromagnetic energy and by the ejection of matter with the solar wind. It is expelling about per year. The mass loss rate will increase when the Sun enters the red giant stage, climbing to y−1 when it reaches the tip of the red-giant branch. This will rise to y−1 on the asymptotic giant branch, before peaking at a rate of 10−5 to 10−4 y−1 as the Sun generates a planetary nebula. By the time the Sun becomes a degenerate white dwarf, it will have lost 46% of its starting mass. The mass of the Sun has been decreasing since the time it formed. This occurs through two processes in nearly equal amounts. First, in the Sun's core, hydrogen is converted into helium through nuclear fusion, in particular the p–p chain, and this reaction converts some mass into energy in the form of gamma ray photons. Most of this energy eventually radiates away from the Sun. Second, high-energy protons and electrons in the atmosphere of the Sun are ejected directly into outer space as the solar wind and coronal mass ejections. The original mass of the Sun at the time it reached the main sequence remains uncertain. The early Sun had much higher mass-loss rates than at present, and it may have lost anywhere from 1–7% of its natal mass over the course of its main-sequence lifetime. The Sun gains a very small amount of mass through the impact of asteroids and comets. However, as the Sun already contains 99.86% of the Solar System's total mass, these impacts cannot offset the mass lost by radiation and ejection. One solar mass, , can be converted to related units:  It is also frequently useful in general relativity to express mass in units of length or time. The solar mass parameter ("G"·), as listed by the IAU Division I Working Group, has the following estimates:   Use–mention distinction  The use–mention distinction is a foundational concept of analytic philosophy, according to which it is necessary to make a distinction between a word (or phrase) and it, and many philosophical works have been "vitiated by a failure to distinguish use and mention". The distinction is disputed by Jacques Derrida. The distinction between use and mention can be illustrated for the word "cheese":  The first sentence is a statement about the substance called "cheese": it "uses" the word 'cheese' to refer to that substance.