Are you using ‘were’ in the indicative or subjunctive?

Because of the extended Covid-19 lockdown, there should be time aplenty for everyone to internalize the answer to this grammar question that I know still stumps many English learners and even long-time users: “How do we know if a sentence that uses ‘were’ is indicative or subjunctive?”

To start this grammar refresher, recall that “were” is the familiar past-tense form of the linking verb “be” in the third-person plural. For example, in the sentence “His ailing sisters were confident of full recovery,” “be” takes the form “were” because the subject “sisters” is in the third-person plural and the action is in the past tense. (Of course, when the subject is the third-person singular “sister” and the statement is in the present tense, “be” takes the normal form “is”: “His ailing sister is confident of full recovery.”)