What word does your mother always say?
1520s, "mood employed to denote an action or state as conceived and not as a fact," from Late Latin subjunctivus "serving to join, connecting," from past participle stem of subjungere "to append, add at the end, place under," from sub "under" (see sub-) + jungere "to join" (see jugular). The Latin modus subjunctivus probably is a grammarians' loan-translation of Greek hypotaktike enklisis "subordinated," so called because the Greek subjunctive mood is used almost exclusively in subordinate clauses.
A grammatical form of verbs implying hypothetical action or condition. Subjunctives are italicized in these sentences: “If Mr. Stafford were [not “was”] fluent in French, he could communicate with his employees more effectively”; “If Sheila had been here, she would have helped us with our math.”