Individual quarks have fractional electric charges. However, these fractional charges are never directly observed because quarks never hang out alone; instead, quarks will form composite particles called hadrons. The sum of the quarks' electric charges in a hadron is always an integer number. While individual quarks carry color charge, hadrons are color-neutral.

There are two classes of hadrons:

Baryons:

Baryons are any hadron made of three quarks (qqq). For example, protons are 2 up quarks and 1 down quark (uud) and neutrons are 1 up and 2 down quarks (udd).

Mesons:

Mesons contain one quark () and one antiquark (). For example, a negative pion () is ().