1. the subject of theoretical grammar its relations to other branches of linguistics

Copulative, connecting two members and their meanings, the second member indicating an addition of equal importance, or, on the other hand, an advance in time and space, or an intensification, often coming in pairs, then called correlatives: and; both... and; equally... and; alike... and; at once... and; not... nor for neither, or and neither); not (or never)... not (or nor)... either; neither... nor, etc.
Disjunctive, connecting two members but disconnecting their meaning, the meaning in the second member excluding that in the first: or, and in questions whether... or with the force of simple or; or... either; either... or, etc., the disjunctive adverbs else, otherwise, or... or, or... else, in older English other else.
Adversative, connecting two members, but contrasting their meaning: but, but then, only, still, yet, and yet, however, on the other hand, again, on the contrary, etc.
Causal, adding an independent proposition explaining the preceding statement, represented only by the single conjunction for: The brook was very high, for a great deal of rain had fallen over night.
Illative, introducing an inference, conclusion, consequence, result:
namely, therefore, on that account, consequently, accordingly, for that reason, so, then, hence, etc.
Explanatory, connecting words, phrases or sentences and introducing an explanation or a particularisation: namely, to wit, that is, that is to say, or, such as, as, like, for example, for instance, say, let us say, etc.

50. SYNTAX AS A BRANCH OF LINGUISTICS

o Syntax as part of grammar.
o The subject matter of Syntax. Syntax deals with combinability of words, i.e. how words are combined to make meaningful utterances, what patterns they combine on, and what abstract grammatical meaning they express.
o The main objectives of Syntax are:
to study relations between words within word combinations;
to study the sentence as a structural unit which communicates a message in a definite situation.
o The units of syntactic analysis are the sentence and the phrase. They repre­sent different levels of a hierarchy.
o From the constructive point of view both the sentence and the phrase are groups of elements related with each other and organised in a definite way.
Syntax, originating from the Greek words συν (syn, meaning "co-" or "together") and τάξις (táxis, meaning "sequence, order, arrangement"), can in linguistics be described as the study of the rules, or "patterned relations" that govern the way the words in a sentence come together. It concerns how different words (which, going back to Dionysios Thrax, are categorized as nouns, adjectives, verbs, etc.) are combined into clauses, which, in turn, are combined into sentences. Syntax attempts to systematize descriptive grammar, and is unconcerned with prescriptive grammar (see Prescription and description).
There exist innumerable theories of formal syntax — theories that have in time risen or fallen in influence. Most theories of syntax at least share two commonalities: First, they hierarchically group subunits into constituent units (phrases). Second, they provide some system of rules to explain patterns of acceptability/grammaticality and unacceptability/ungrammaticality. Most formal theories of syntax offer explanations of the systematic relationships between syntactic form and semantic meaning.
There are various theories as to how best to make grammars such that by systematic application of the rules, one can arrive at every phrase marker in a language (and hence every sentence in the language).
A modern approach to combining accurate descriptions of the grammatical patterns of language with their function in context is that of systemic functional grammar, an approach originally developed by Michael A.K. Halliday in the 1960s and now pursued actively in all continents. Systemic-functional grammar is related both to feature-based approaches such as Head-driven phrase structure grammar and to the older functional traditions of European schools of linguistics such as British Contextualism and the Prague School.
A syntactic category is either a phrasal category, such as noun phrase or verb phrase, which can be decomposed into smaller syntactic categories, or a lexical category, such as noun or verb, which cannot be further decomposed.
In terms of phrase structure rules, phrasal categories can occur to the left side of the arrow while lexical categories cannot.
The lexical categories are traditionally called the parts of speech. They include nouns, verbs, adjectives, and so on.