The logic of an article or paper does depend on the structuring in terms of appropriate levels or units needs to have an internal consistency. consistency may be reflected (or missing) on two different levels, cohesion and coherence. Cohesion is more easily identifiable achievable than coherence. mainly relates to a writer’s ability of linking the individual parts of the document properly by using appropriate connectors, anaphoric or cataphoric expressions, etc., to make the text flow more smoothly and to mark temporal or causal relations. that is at least partly related to cohesion is the use of commas, with regard to adverbial phrases or lists, etc. or the appropriate use of easy to process co- or subordinated structures. types of punctuation may also sometimes present problems, the use of semicolons or colons, their adequate use is often more difficult to explain.
Coherence often has even more to do with the appropriate ordering of information and sense. may be related to issues of punctuation, other issues, the use of conditional clauses, co- and sub-ordination, may go down to even the lowest level at the discourse hierarchy, the use of appropriate words or idiomatic expressions. Lack of coherence, other than simply making it a little less difficult to understand a text, as would usually be the case with lack of cohesion, can often render parts of the text unintelligible and tends to lead to more critical errors.