Kids.Net.Au

Kids.Net.Au is a "search engine for kids, children, parents, educators and teachers" and includes its own dictionary, thesaurus, and encyclopedia services. It even has some information on...you guessed it: quarks!

The Kids.Net.Au dictionary defines a quark as a "hypothetical truly fundamental particle in mesons and baryons; there are supposed to be six flavors of quarks (and their antiquarks), which come in pairs; each has an electric charge of +2/3 or -1/3", and also lists hyponyms and translations for "quark" into 25 other languages!

The encyclopedia entry offers a summary of the history of quarks and their discovery.