Subjects and verbs must agree in number. This is the cornerstone rule that forms the background of the concept. The dog growls when he is angry. The dogs growl when they are angry. Don’t get confused by the words that come between the subject and verb
Sorry, grammar nerds. The singular ‘they’ has been declared Word of the Year.
Everyone Uses Singular 'They,' Whether They Realize It Or Not (The singular, gender-neutral usage of "they" is now acceptable on college campuses, among the genderqueer and in the Washington Post. Linguist Geoff Nunberg traces the rise of the new "they.