We can all speak and understand each other; do we need to investigate how?

5.7 The simple nominal predicate

The simple nominal predicate is expressed by a noun, or an adjective, or a verbal, ft does not contain a link verb, as it shows the incompatibility of the idea expressed by the subject and that expressed by the predicate; thus in the meaning of the simple nominal predicate there is an implied negation.

He a gentleman! You a bother! Never.

Ну какой же он джентльмен! Ты - зануда! Ну, что ты!

Sentences with the simple nominal predicate are always exclamatory evidently owing to the implication of a negation or of an evaluation.
The predicate is mostly commad off (separated by a comma), but a comma is not regarded as a strict rule.
These predicates are used in colloquial English, although not fre­quently.

5.8 The compound predicate

The compound predicate consists of two parts: the notional and the structural. The structural part comes first and is followed by the notional part.
The notional part may be expressed by a noun, an adjective, a stative, an adverb, a verbal, a phrase, a predicative complex, or a clause.
The structural part is expressed by a finite verb - a phasal verb, a modal verb, a verb expressing attitude, intention, planning, etc., or a link verb.
From the point of view of meaning the most important part of the compound predicate is the notional part as it contains the information about the person or non-person expressed by the subject.
From the point of view of structure the most important part of the predicate is the first one, since it is expressed by a finite verb and carries grammatical information about the person, number, tense, voice, modal, attitudinal and aspective (phasal) meaning of the whole predicate.