Word choice or vocabulary. Diction refers to the class of words that an author chooses as appropriate for a particular work.
Words that specifically name or describe things or persons.
Concrete words refer to what we can immediately perceive with our senses.
Words that express general ideas or concepts
Strictly speaking, poetic diction means any language deemed suitable for verse, but the term generally refers to elevated language intended for poetry rather than common use.
A brief, sometimes indirect, reference in a text to a person, place, or thing. Allusions imply a common body of knowledge between reader and writer and act as a literary shorthand to enrich the meaning of a text.