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

suffixes – derivational affixes following the stem and forming a new derivative within the same part of speech (e.g. king-dom, book-let, child-hood etc.) or in a different word class (e.g. do-er, wash-able, sharp-en etc.);
infixes – affixational morphemes placed within a word, e.g –n– in stand.
According to their functions and meaning, affixes fall into:
derivational, e.g. suffixes: abstract-noun-makers (-age, -dom, -ery, -ing, -ism); concrete-noun-makers (-eer, -er, -ess, -let); adverb-makers (-ly, -ward(s), -wise); verb-makers (-ate, -en, -ify, -ize/-ise); adjective-/noun-makers (-ful, -ese, -(i)an, -ist), etc.; they are attached to a derivational base; they are the object of study of derivational morphology which investigates the way in which new items of vocabulary can be built up out of combinations of elements;
functional (inflectional), e.g. -s (plurality; 3rd person singular); ‘s (genitive case); -n’t (contracted negative); -ed (past tense; past participle); -ing (present participle); -er, -est (comparison); they are attached to a morphological stem; they are the object of study of inflectional morphology which deals with the way words vary in their form in order to express a grammatical contrast.
derivational affixes
encode lexical meaning;
are syntactically irrelevant;
can occur inside derivation;
often change the part of speech;
are often semantically opaque;
are often restricted in their productivity;
are not restricted to suffixation.
inflections
encode grammatical meaning;
are syntactically relevant;
occur outside all derivation;
do not change part of speech;
are rarely semantically opaque;
are fully productive;
are always suffixational (in English).
A lexicalised grammatical affix is an inflection which developed into a derivational suffix.
For example:
–s in customs ‘import duties’, colours ‘a flag / flags of a ship’ does not express plurality;
‘s in at the dentist’s, at my friend’s no longer indicates possession.
13. The derivative structure of English words. The distinction between morphological stem and derivational base. Morphemic analysis vs derivational analysis.
A morpheme (Gr. morphé ‘form, shape’) is one of the fundamental units of a language, a minimum sign that is an association of a given meaning with a given form (sound and graphic), e.g. old, un+happy, grow+th, blue+colour+ed.