Branches of linguistics. Synchronic vs diachronic approaches to the language study. Lexicology – ‘the science of the word’

A thematic group is a subsystem of the vocabulary for which the basis of grouping is not only linguistic but also extralinguistic: the words are associated because the things they name occur together and are closely connected in reality, e.g.:
-terms of kinship: father, cousin, mother-in-law, uncle;
-names for parts of the human body: head, neck, arm, foot, thumb;
-colour terms: blue, green, yellow, red / scarlet, crimson, coral;
-military terms: lieutenant, captain, major, colonel, general.
An ideographic group unites thematically related words of different parts of speech; here words and expressions are classed not according to their lexico-grammatical meaning but strictly according to their signification, i.e. to the system of logical notions, e.g.: ‘Trade’: to buy, to sell, to pay, to cost, a price, money, cash, a receipt, expensive etc.
As a rule, ideographic groups deal with contexts on the level of the sentence. Words in ideographic groups are joined together by common contextual associations within the framework of the sentence and reflect the interlinking of things or events, e.g.:
‘Going by train’: railway, a journey, a train, a train station, timetable, a platform, a passenger, a single ticket, a return ticket, luggage, a smoking carriage, a non-smoking carriage, a dining-car, to enquire, to catch the train, to miss the train etc.
A semantic field is the extensive organisation of related words and expressions into a system which shows their relations to one another.
The significance of each unit is determined by its neighbours, with the units’ semantic areas reciprocally limiting each other.
The members of the semantic fields are joined together by some common semantic component known as the common denominator of meaning.
‘Human Mind’: mind, reason, cognition, idea, concept, judgment, analysis, conclusion;
A lexico-semantic group is singled out on purely linguistic principles: words are united if they have one or more semantic components in common, but differ in some other semantic components constituting their semantic structures. The
This type of groupings is mostly applied to verbs, e.g.
-verbs of sense perception: to see, to hear, to feel, to taste;
-verbs denoting speech acts: to speak, to talk, to chat, to natter, to mumble, to ramble, to stammer, to converse;
-verbs of motion: to walk, to run, to tiptoe, to stroll, to stagger, to stomp, to swagger, to wander.
26. Dynamics of the English vocabulary. Neologisms: their sources and formation.
Language is never stationary. New words are constantly being formed; living words are constantly changing their meanings, expanding, contracting, gaining or losing caste, taking on mental, moral, or spiritual significance; and old words, though long sanctioned by custom, sometimes wither and die.