4. Style
From 'How To Use the 'ABC Of Plain Words' by E Gowers (1951)

Articles that give guidance about this and are not easily classifiable under any more specific label are :—

Abstract words (addiction to)
Adjectives (proper use of)
Adverbs (proper use of)
Arrangement
Cliché
Commercialese
Explanation (what to aim at and what to avoid in explaining)
Gobbledygook (a general section)
Idiom
Jargon
Metaphor
Noun adjectives
Padding
Parenthesis
Phrasal verbs
Prepositions (circumlocutory substitutes for)
Qualification of Absolutes (very unique)
Sentences
Verbal particles (see Phrasal verbs)