Idioms, phraseological units. Phraseological expressions and their types

Quotations
Next to the originator of a good sentence is the first quoter of it. Emerson
A quotation is a repetition of a phrase or statement from a book, speech and the like used by way of authority, illustration, proof or as a basis for further speculation on the matter in hand.
By repeating a passage in a new environment, we attach to the ut­terance an importance it might not have had in the context whence it was taken. Moreover, we give it the status, temporary though it may be, of a stable language unit. What is quoted must be worth quoting, since a quotation will inevitably acquire some degree of generalization. If repeated frequently, it may be recognized as an epigram, if, of course, it has at least some of the linguistic properties of the latter.
Quotations are usually marked off in the text by inverted commas (" "), dashes (—), italics or other graphical means.
They are mostly used accompanied by a reference to the author of the quotation, unless he is well known to the reader or audience. The reference is made either in the text or in a foot-note and assumes va­rious forms, as, for instance:
"as (so and so) has it"; "(So and so) once said that"...; "Here we quote (so and so)" or in the manner the reference to Emerson has been made in the epigraph to this chapter.
A quotation is the exact reproduction of an actual utterance made by a certain author. The work containing the utterance quoted must have been published or at least spoken in public; for quotations are echoes of somebody else's words.
Quotations are also used in epigraphs. The quotation in this case possesses great associative power and calls forth much connotative mean­ing,