5.B Unity and Coherence at Three Levels (REO-1.N)

Coherence is not one switch, it is three. Inside a clause, words have to hang together grammatically. Inside a sentence, clauses have to connect logically, usually with a conjunction or punctuation doing the connecting work. Across a paragraph, sentences have to link to each other, each one picking up a word, an idea, or a pronoun from what just came before. A paragraph can be perfect at the first two scales and still fail at the third, because nothing stops a writer from stringing together clean, well-formed sentences that never actually touch.

Unity and coherence answer different questions. Unity asks whether a sentence belongs in this paragraph at all, whether it serves the paragraph's one governing idea. Coherence asks whether a reader can move from one sentence to the next without having to guess the connection. A sentence can be perfectly unified, clearly on topic, and still wreck the coherence of the paragraph if it drops in with no link to the sentence before it. That is why swapping in a transition word like 'however' or 'therefore' does not fix a broken stretch on its own. A transition only works if it names a connection that is actually there; stapled onto sentences with no real relationship, it just adds a word without adding a link.

This is why a cut sentence can cause damage far from where the scissors went in. Paragraphs often build chains, where sentence 5 leans on a term or idea planted back in sentence 3. Delete sentence 3, and sentence 5's reference, maybe a pronoun like 'this' or 'it', now points at nothing. The paragraph looks locally fine right around the cut, but coherence breaks two steps downstream. Reading for coherence means checking every sentence against its neighbor, not just scanning for grammar.