[*] 193. A Periphrastic form, as the name indicates, is a “roundabout way of speaking.” In the widest sense, all verb-phrases consisting of participles and sum are Periphrastic Forms. The Present Participle is, however, rarely so used, and the Perfect Participle with sum is included in the regular conjugation (amātus sum, eram, etc.). Hence the term Periphrastic Conjugation is usually restricted to verb-phrases consisting of the Future Active Participle or the Gerundive with sum.
[*] Note.--The Future Passive Infinitive, as amātum īrī , formed from the infinitive passive of eō, go, used impersonally with the supine in -um, may also be classed as a periphrastic form (§ 203. a).
[*] 286. Adjectives, Adjective Pronouns, and Participles agree with their nouns in Gender, Number, and Case:—
vir fortis, a brave man.
illa mulier, that woman.
urbium māgnārum, of great cities.
cum ducentīs mīlitibus, with two hundred soldiers.
imperātor victus est, the general was beaten.
secūtae sunt tempestātēs, storms followed.
[*] Note.--All rules for the agreement of adjectives apply also to adjective pronouns and to participles.
ptolemyauletes wrote:This is the same as saying that English does not have a future tense. It doesn't! It uses modal verbs or even the present tense with adverbial markers to indicate the future. I will go, I am going, I am about to go, etc
H&P, p.80, wrote:i They are entertaining the prime minister and her husband. [form of verb]
ii The show was entertaining. [participial adjective]
iii Her parents are entertaining. [ambiguous]
Says the angry cook to their late, demanding guest // Ità coquus iratus hospiti sero et hiulco.
i Cane cena manducata est. The meal was eaten by the dog. [form of verb]
ii Cena manducata non jam est. An eaten meal exists no longer. [participial adjective]
Note also, he doesn't say // Nota benè, non dicit autem hoc
iii Cena manducata non est. [ambiguous]
Huddleston & Pullum, on "Adjectival Passives", p.1436, Ch.16, §10.1.3 wrote:i The kitchen window was broken by the thieves. [verbal: be-passive]
ii They were very worried. [adjectival: complex-intransitive]
iii They were married. [ambiguous]
Broken in [i.] is a verb, worried in [ii] is an adjective, while married in [iii] can be either.