An inflected language is one where a great many words change their endings — or sometimes their insides — to show tense, number, case, person, and so on. Latin, Russian, and German are often called inflected languages. Mandarin is not, in this sense: it does not pile endings onto words the same way. English sits in the middle. We still have inflected forms such as children, went, and better, but we also depend on word order and helper words. Though actually, when people say “English is not inflected,” they are exaggerating to make a contrast with Latin; English is simply much less inflected. You will also hear “an inflected form,” meaning one changed shape of a word, like went for go. The word is the adjective (and the -ed form) from inflect, so it lives in grammar books and language classes, not in street talk.