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Generation (particle physics)
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<p> In <a href="/facts/Particle_physics/YgIuyj2t">particle physics</a>, a generation or family is a division of the <a href="/facts/Elementary_particle/CTFDM97U">elementary particles</a>. Between generations, particles differ by their <a href="/facts/Flavour_(particle_physics)/RR7rsuTD">flavour quantum number</a> and <a href="/facts/Mass/HHdc8XmF">mass</a>, but their <a href="/facts/Fundamental_interaction/WrFEJaFl">electric and strong interactions</a> are identical. </p><p>There are three generations according to the <a href="/facts/Standard_Model/LhVGf9ow">Standard Model</a> of particle physics. Each generation contains two types of <a href="/facts/Lepton/X4a6MGop">leptons</a> and two types of <a href="/facts/Quark/hwuuVkV5">quarks</a>. The two leptons may be classified into one with <a href="/facts/Electric_charge/xxsBfmlB">electric charge</a> −1 (electron-like) and neutral (neutrino); the two quarks may be classified into one with charge −1⁄3 (down-type) and one with charge +2⁄3 (up-type). The basic features of quark–lepton generation or families, such as their masses and mixings etc., can be described by some of the proposed <a href="/facts/Family_symmetries/0swLGX6R">family symmetries</a>. </p> Generations of matter<table><tbody><tr><th colspan="2"><a href="/facts/Fermion/LEckdDsR">Fermion</a> categories</th><th colspan="3"><a href="/facts/Elementary_particle/CTFDM97U">Elementary particle</a> generation</th></tr><tr><th> <i>Type</i> </th><th> <i>Subtype</i> </th><th> <i>First</i> </th><th> <i>Second</i> </th><th> <i>Third</i> </th></tr><tr><th rowspan="2"><a href="/facts/Quark/hwuuVkV5">Quarks</a>(<a href="/facts/Color_(quantum_mechanics)/aWS1xsCR">colored</a>)</th><th>down-type</th><td><a href="/facts/Down_quark/Nq10ayEE">down</a></td><td><a href="/facts/Strange_quark/VDWd3ky0">strange</a></td><td><a href="/facts/Bottom_quark/2s4rJRSo">bottom</a></td></tr><tr><th>up-type</th><td><a href="/facts/Up_quark/Aw3Vp3vk">up</a></td><td><a href="/facts/Charm_quark/RLduBtpL">charm</a></td><td><a href="/facts/Top_quark/82qd7NPI">top</a></td></tr><tr><th rowspan="2"><a href="/facts/Lepton/X4a6MGop">Leptons</a> (color-free) </th><th>charged </th><td><a href="/facts/Electron/L0KBo5cW">electron</a></td><td><a href="/facts/Muon/BP2fLVIR">muon</a></td><td><a href="/facts/Tau_(particle)/6DW8j6PC">tau</a></td></tr><tr><th> <a href="/facts/Neutrino/yGWVfSg2">neutral</a> </th><td> <a href="/facts/Electron_neutrino/e5hQPWIQ">electron neutrino</a> </td><td> <a href="/facts/Muon_neutrino/A8kPHDKd">muon neutrino</a> </td><td> <a href="/facts/Tau_neutrino/GGIb4W5b">tau neutrino</a> </td></tr></tbody></table>