1.The antiparticle of a neutron.
‘Antimatter is matter composed of antiparticles, such as positrons, antineutrons and antiprotons.'
‘The antineutron, although neutral like the neutron, is distinguishable from the neutron because it is composed of two anti-down quarks and one anti-up quark.'
‘Antimatter also exists and so there is an antiproton, an antineutron and an antielectron often called the positron.'
‘One can imagine atoms that are made of antiparticles: antiprotons, antineutrons, and positrons.'
‘The antineutron contains one anti-up quark and two anti-down quarks, giving it a charge of 0, just like the regular neutron.'