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All are fine except Voc. Sing. of Filius bonus. Any masculine -us noun of the second declension has the end -e, i.e Marce = O Marcus. Thus also with 1st/2nd declension masc. adjectives. So combined with the vocative "mi fili" (voc of meus) "bone mi fili" or whatever order for emphasis. And also praesidiis in dat/abl plural, they do retain their i.
The loss of the -i- in any case is a Ciceronian feature. You can decide whether you want to do it or not in your own writing, since both were at use during different times, but still within the period of Classical Latin.
As Episcopus said, the vocative of nouns in -ius just drops the us and makes the i long (fili). Be careful though, since this is not the case with the few adjectives that end in -ius: they merely follow the normal pattern of ending in -e. So, the adjective eximius has as its vocative eximie.
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae
Just accept what D'Ooge says about these (he makes a whole lesson upon this) and you will not need to worry about any minor irregularities (for they are only minor; verbal principal parts for example are far far harder).
All are fine except Voc. Sing. of Filius bonus. Any masculine -us noun of the second declension has the end -e, i.e Marce = O Marcus
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DO'odge p.38 section 89 gives the vocative singular of filius as fili. However, I would say the adjective bona would be in the form bone since it is describing a masculine noun in the vocative singular.
After reviewing it a little more I think that this is a little more correct:
Singular
Nom - praesidium parvum
Gen - praesidi parvi
Acc - praesidium parvum
Dat - praesidio parvo
Abl - praesidio parvo
Voc - praesidium parvum
Plural
Nom - praesidia parva
Gen - praesidiorum parvorum
Acc - praesidia parva
Dat - praesidiis parvis
Abl - praesidiis parvis
Voc - praesidia parva
Singular
Nom - filius bonus
Gen - fili boni
Acc - filium bonum
Dat - filio bono
Abl - filio bono
Voc - fili bone
Plural
Nom - filii boni
Gen - filiorum bonorum
Acc - filios bonos
Dat - filiis bonis
Abl - filiis bonis
Voc - filii boni
Yes it's usually easy to tell by context. Obviously fili takes an irregular vocative in a similar way to meus, my - mi. Watch out "Deus" vocative is "Deus".
You are astute to notice that even with heavy inflection case can be ambiguous. You often cannot determine 'case' (in the sense of the role a noun is playing) from ending alone.
Many 2nd (puer, magister), all (IIRC) neuter and all 3rd, 4th and 5th declension nouns lack distinctive vocatives. To have a distinct vocative turns out to be rather the exception than the rule, and you might find it easier not to bother learning them, or only to learn them when they are both common and distinctive. (That, after all, is what one does with cases such as the locative, and the vocative is hardly common and usually obvious.)
More significantly, since they are more common and cover what more seemingly important semantic distinctions: neuter nouns do not distinguish between nominative and accusative (a pretty fundamental semantic distinction); dative and ablative plurals are invariably the same regardless of gender; the second declension has the same dative and ablative singular; the first and fourth declensions have the same dative and genitive singular (and first declension genitive singular = first declension nominative/vocative plural). Fourth declension singular neuter nouns hardly decline at all, you will be pleased to hear.
All of which goes to show that -- contrary to the neat impression one may get at first, and which the first and second declensions sort of play to -- ending does not invariably enable one to work out what case a noun is. Latin can be ambiguous too. Context and the rest are often important, and occasionally there may be real doubt about how a particular word should be understood.
Ulpianus wrote:You are astute to notice that even with heavy inflection case can be ambiguous. You often cannot determine 'case' (in the sense of the role a noun is playing) from ending alone.
Agreed. The first time I read "Non scholae sed vitae discimus", I thought it meant "We don't learn from the school, but from life."