Are these two different names for the same thing or are they different concepts depending on the context?
They’re essentially the same thing as far as I know. The same idea is actually very similar to English. Here’s an example:
Lēgēs pārendae sunt. - In a sense, “The laws are to be obeyed”. The future & passive aspect sort of merges with the obligatory gerundive accent.
Let me add a reply.
The gerundive/future passive participle has two different meanings/functions, depending on context. Although these two different meaning/functions might have originally had forms distinct from each other, they have identical forms in the Latin we see. Whichever name is chosen is often sometimes applied to the form regardless of its contextual meaning or function.
One function of the form has the same meaning as the gerund, but has a different syntactic construction. Having the same meaning as the gerund presumably justifies calling the form “gerundive” to indicate the relationship.
An example of this function from Moreland and Fleisher is: Librīs legendīs legere discimus, which has the same meaning as this sentence with a gerund: Librōs legendō legere discimus (We learn to read by reading books).
The other function refers to a meaning that general refers to future action and is arguable interpreted as a passive. It is a verbal adjective with the semantics of a verb but the syntax of an adjective. These three factors could justify calling the form a “future passive participle”; however, such a term fails to capture the meaning of “obligation, necessity, or propriety” that is essential to this function. Calling the form merely a “future passive participle” is thus misleading even for this function.
An example of this function from Moreland and Fleisher is: Librōs legendōs in mensā posuit (He placed the books which were to be read on the table).
Neither terminology for the form captures both uses; however, I believe most grammars prefer the term “gerundive,” presumably because it is less misleading and at least captures one meaning. Moreland and Fleisher does call the first function a “gerundive” and the second a “future passive participle,” but I do not think this terminological distinction is universal or necessarily even common among current grammars. I don’t know of another handy way to differentiate the meanings/functions unambiguously but would describe them perhaps as a (1) verbal adjective used instead of a gerund or (2) verbal adjective expressing necessity.
Oh right, I forgot about this important use of the gerundive, which is even more common than the equivalent gerund construction (I think). Thanks for including that!
I apologise in advance if I be wrong, but since pareo is an intransitive verb, I do not believe that it can be turned around into the passive so easily - that quality belongs only to transitive verbs. Unless my textbooks have misled me, the gerundive of an intransitive verb can only be used impersonally, so:
'The laws are to be obeyed ’ should, I think, be rendered in Latin as, 'legibus parendum est ', literally, ‘There is an-act-of-obedience-to-be-done to the laws’.
I am happy to be corrected if mistaken.
You are right.
Oh, yes. Thank you for that correction!