Why was the subjunctive mood 'so called because the Greek subjunctive mood is used almost exclusively in subordinate clauses'?

Question

Concerning the adjective "subjunctive", OED (3rd ed., 2012) mentions (emphasis mine):

Post-classical Latin subiunctivus is a translation equivalent of Hellenistic Greek ὑποτακτικός , which as a grammatical term was used variously with the meaning ‘subjoined’. With subjunctive mood (see sense A. 1a; compare sense B. 1) compare post-classical Latin modus subiunctivus (3rd cent.), Hellenistic Greek ὑποτακτικὴ ἔγκλισις . [1.] The subjunctive mood was so called because it was regarded as specially appropriate to ‘subjoined’ or subordinate clauses. In the Latin grammarians the more common term for subjunctive was post-classical Latin coniunctivus conjunctive adj.; subiunctivus is the term favoured by Priscian (5th-6th cent.).

Etymonline describes the etymology of the word and also mentions:

The Latin modus subiunctivus probably is a loan-translation by the grammarians of Greek hypotaktike enklisis "subordinated," [2.] so called because the Greek subjunctive mood is used almost exclusively in subordinate clauses.

Can someone please expound and enlarge on this sentence? Why was the subjunctive mood 'regarded as specially appropriate to ‘subjoined’ or subordinate clauses'?

Why was the Greek subjunctive mood 'used almost exclusively in subordinate clauses'? Couldn't it have been used almost exclusively in independent clauses?

Answer 1

Can someone please expound and enlarge on this sentence? Why was the subjunctive mood 'regarded as specially appropriate to ‘subjoined’ or subordinate clauses'?

Perhaps you are looking at it the wrong way around. Language happens to be what it is and we describe it, but our descriptions have little or no effect on the language. If we declared subjunctive mood inappropriate for subordinate clauses, people would still speak the way they do. This mood was used long before grammarians started giving it names. The point is that "specially appropriate for subordinate clauses" means "found most commonly in subordinate clauses". It would have been clearer if worded that way.

The word "subjunctive" comes from the participle subiunctus ("subjugated", "subjoined", and similar). The passage you quote suggests that the name for this form mood is due to its frequent appearance in subordinate clauses. Even if it has other uses as well, subordination requiring this mood makes "subjunctive" a good name.

Why was the Greek subjunctive mood 'used almost exclusively in subordinate clauses'? Couldn't it have been used almost exclusively in independent clauses?

Why was genitive used for possession? What was perfect tense used for past events? Why was subjunctive used for subordinate clauses? That's just the way it happens to be. Grammar questions with "why" don't often have very meaningful answers, and I don't think this one has either. But since the use of moods, cases, and others is so consistent, we can be sure that the rules do exist.

According to this text, this Greek mood happens to be used in subordinate clauses almost exclusively. It is similar in Latin, although "almost exclusively" might be a little too strong. Many kinds of subordination (like indirect questions) automatically require this mood in Latin. I don't think there is a satisfying answer to "why". Grammar isn't a theory where you can logically deduce things from others. It is primarily a description of how a language is actually used. And this description here is: "this mood is found mainly in subordinate clauses and we call it 'subjunctive' for that reason".

Answer 2

As Joonas quite aptly put it:

I don't think there is a satisfying answer to "why". Grammar isn't a theory where you can logically deduce things from others. It is primarily a description of how a language is actually used. And this description here is: "this mood is found mainly in subordinate clauses and we call it 'subjunctive' for that reason".

This is absolutely true and correct. But to come at your question from a different angle…

The Latin subjunctive/conjunctive mood was used in all sorts of different environments. It was used for suggestions, for hopes, for less-vivid conditionals, and various other independent uses, along with subordinate clauses. For example, 2 Timothy 1:16:

Det misericordiam Dominus Onesiphori domui
May the Lord grant mercy to the house of Onesiphorus

In Greek, most of these roles are filled by the optative instead, a mood that Classical Latin lacks. (Optative = optātivus = "for wishing".)

Δῴη ἔλεος ὁ κύριος τῷ Ὀνησιφόρου οἴκῳ
May the Lord grant mercy to the house of Onesiphoros

Thus, the Greek subjunctive appears in independent clauses significantly less than the Latin one does, since a Latin subjunctive main verb often translates to an optative in Greek. Subjunctive main verbs do still appear sometimes, like for hortatory sentences ("let's ___!"), but they're not a common sight.