Register refers to the level of formality in language, and grammar varies by register. Formal writing avoids contractions ("do not" instead of "don't"), uses passive voice more often ("It was determined that..."), and employs complex sentence structures. Informal speech uses contractions, active voice, and simpler structures. Appropriate register depends on audience and context.
Compare formal and informal versions of the same idea and notice grammatical differences. Practice adjusting register by expanding contractions, shifting voice, and varying sentence complexity.
Register is the grammar of social context: the set of linguistic choices a speaker or writer makes to signal their relationship to the audience, the occasion, and the subject matter. You already understand active and passive voice as two options for framing a sentence — and register is the larger system that governs which option is appropriate when. Formal register does not mean "correct" register. It means register calibrated for high-stakes, professional, or institutional contexts where distance, precision, and authority are valued.
The grammatical markers of formal register cluster into three categories. First, expansion over contraction: formal writing writes out "do not," "it is," "they have been," rather than collapsing them. Contractions signal proximity and informality; expanding them signals care and deliberateness. Second, passive voice and nominalization: formal prose often prefers "It was determined that the project would be delayed" over "We decided to delay the project." The passive voice removes the actor, which can signal objectivity or diffuse responsibility — both valued in institutional writing. Nominalizations (turning verbs into nouns: "make a determination" instead of "determine," "conduct an analysis" instead of "analyze") add an additional layer of abstraction that reads as academic or official. Third, syntactic complexity: longer sentences with embedded clauses, more precise vocabulary, and explicit logical connectors ("therefore," "consequently," "notwithstanding") all raise formality.
Informal register runs in the opposite direction on every axis. Contractions appear freely. Active voice dominates. Sentences are shorter and more direct. Vocabulary is drawn from everyday speech, not specialized or Latinate sources. Colloquialisms, sentence fragments, and even slang are permissible when context supports them. Neither pole is superior — a wedding toast written in bureaucratic passive voice is just as wrong as a legal brief written in slang.
The key skill is register awareness: diagnosing the context and audience, then producing language that fits. Every writing decision you make — whether to write "cannot" or "can't," whether to frame a sentence actively or passively, whether to use "use" or "utilize" — is a micro-choice about register. Skilled writers are not locked into one register; they can shift fluidly, and they notice when someone else has pitched their register wrong for the room. Practice this by taking a single paragraph and deliberately rewriting it in the opposite register — formal to informal, informal to formal — paying attention to exactly which features you change at each step.