subjunctive (n.)

"mood employed to denote an action or state as conceived and not as a fact," 1620s, from earlier adjectival use of subjunctive (1520s), from Late Latin subiunctivus "serving to join, connecting," from subiunct-, past participle stem of Latin subiungere "to append, add at the end, place under," from sub "under" (see sub-) + iungere "to join together" (from nasalized form of PIE root *yeug- "to join"). The Latin modus subiunctivus probably is a loan-translation by the grammarians of Greek hypotaktike enklisis "subordinated," so called because the Greek subjunctive mood is used almost exclusively in subordinate clauses.

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Definitions of subjunctive from WordNet
subjunctive (n.)
a mood that represents an act or state (not as a fact but) as contingent or possible;
Synonyms: subjunctive mood
subjunctive (adj.)
relating to a mood of verbs;
subjunctive verb endings