2.3. Language taxonomy and the concept of the unit structure

Everything in this world has its structure. Taxonomy means classification of the units that is based on their complex hierarchical relations; it is organized by supertype-subtype relationships, also it is called generalization-specialization relationships, or less formally, parent-child relationships. In such an inheritance relationship, the subtype by definition has the same properties, behaviors, and constraints as the supertype plus one or more additional properties, behaviors, or constraints. For example, car is a subtype of vehicle. So any car is also a vehicle, but not every vehicle is a car. Therefore, a type needs to satisfy more constraints to be a car than to be a vehicle. Another example, any shirt is also a piece of clothing, but not every piece of clothing is a shirt. Hence, a type must satisfy more parameters to be a shirt than to be a piece of clothing.

Thus, the term 'language structure' is referred to the relationships that exist between the small units that make up a larger unit. For example, the basic conceptual components of a table are ‘a flat board’ and ‘four long thin pieces of wood or metal’, but these elements do not constitute a structure until they are related to each other logically. In this way, each 'element' is given its position and its function, which together may be called the 'grammatical feature' of every member of the class that relates it to a more general class of words (category). Linguistic structures are described in terms of language units with their morphological markers, semantic functions within and syntactic relationships with each other within the clause.

2.3.1. Syntactic elements of clauses

In traditional linguistics a sentence is often defined as a grammatical unit consisting of one or more words that are generally logically and grammatically tied thus bearing minimal syntactic relation to the words that precede or follow it.

By structure grammarians distinguish simple (consisting of a single independent clause), compound (consisting of multiple independent clauses with no dependent clauses), complex (consisting of at least one independent clause and one dependent clause) or complex-compound sentences (consisting of multiple independent clauses at least one of which has one dependent clause).

The main (minimal) structure of a sentence is labeled a clause. It consists of two major constituents – a subject and a predicate. The subject is typically a noun group, though other classes of word groups can work as well (such as a gerund group) or the subject may be omitted by the speaker. The predicate is a finite verb group – a finite verb together with zero or more objects, complements or adverbials. Within a sentence we distinguish major or minor clauses. A major clause means a regular sentence with its subject and predicate (She had a son). In this sentence one can change the persons, time of the action: I have a son. However, a minor clause is marked by irregularity of the structure – it may not contain a finite verb (for ex.: "Mary!" "Yes." "Coffee." etc.). Other examples of minor clauses are headings in articles or books, stereotyped expressions (Hello!), emotional expressions (Wow!), proverbs, etc. This can also include nominal clauses like The more, the merrier. These do not contain verbs in order to intensify the meaning around the nouns and are normally found in poetry and catchphrases.

The main function of a clause is to make a frame to represent information about the situation type. By purpose sentences are classified into declarative, interrogative, explanative, imperative sentences or a command. In grammar the declarative type is considered to be the basis for any analysis.

Clauses make consists of a number of syntactic elements of all classes of the unit. The criteria for their identification (the syntactic features) and realization of each class of units will be analyzed in the next chapters. Below there is a review to exemplify typical clause elements within basic clause structures: a subject, a predicate, an object, a complement, an adjunct, a conjunct.

The major clause structure used (syntactic expression of a 'situation' or 'state of affairs') depends greatly on the verbal component of it. (Verb complementation types will be treated later and in full details).

Subject (S)	Fog is dangerous on motorways.	SPCsA
Predicator (P)	The election campaign ended yesterday.	SPA
Direct Object (Od)	Ted has bought a new motorbike.	SPOd
Indirect Object (Oi)	They sent their friend a new single.	SPOiOd
Prepositional Object (Oprep)	He must be looking for this paper.	SPOprep
Subject Complement (Cs)	He is powerless to make any changes.	SPCs
Object Complement (Co)	We consider the situation in Iran alarming.	SPOdCo
Predicator Complement (Cp)	She tiptoed out of the room.	SPCp
Adjunct (A)	The news reached them on Tuesday.	SPOdA
Disjunct (D)	Unfortunately, it was too late to change the provider.	DSPCs
Conjunct (Conj)	However, other friends were with us.	ConjSPA