I have been studying Crosby's "An Introduction to Greek" and using Sidgwick's "A First Greek Writer." In both of these texts, they explain about the attributive adjective and the predicate adjective. The attributive adjective is really easy to understand; there is no room for confusion. The predicate adjective is giving me a little trouble.
The way both authors explained predicate adjectives, it sounds as if a being verb does not have to be included. Indeed, the examples don't use a being verb and yet are translated with "is." Unfortunately, Sidgwick complicates the matter by, in the answer key, using being verbs every instance of predicate adjectives (in the first reading. I haven't worked further yet). This wouldn't be a problem to me, just an annoying omission on his part in the grammar, except that Crosby offers "ἀρχὴ δέ τοι ἣμισυ παντός" as the opening quote to one of his chapters (V). Based on my initial understanding of predicate adjectives, I thought it said, "The half of everything is a [its] beginning." But Crosby translates it (literally) as "The beginning is half of everything." This confused me terribly, but here is my current understanding, please correct me if I'm wrong:
Predicate adjectives need a being verb unless they are being used in a pithy saying such as "ἀρχὴ δέ τοι παντός." When trying to be sublime and concise, being verbs can be omitted from phrases with predicate adjectives.