Here's a sentence without transitional expressions, taken from the previous Disputed Issues entry:
Plain-writing advocates commonly recommend short paragraphs. Very short paragraphs provide a false sense of Concision, actually compromised by forced redundancy.The second sentence states a proposition opposed to the first. Inserting the stock transition however explicitly expresses the tension between successive clauses:
Very short paragraphs, however, provide a false sense of Concision...However is so good a minimalist example of a transitional expression that, unless you consult definitions, it may not seem an expression. An expression's defining property is diminished semantic content borne of a stale combination of terms. Although however is a single word, it is composed of how and ever and gets its meaning from them figuratively. However vaguely expresses contrariety to the preceding clause.
Connection between sentences is more Concisely carried by sentence structure than expressions. Structural methods call attention to the clauses' relationship without vaguely stating it, as in the example where re-introducing the phrase short paragraphs from the first sentence's predicate in the second sentence's subject relates the sentences. Worse than the prolixity of unneeded expressions or the cacophony of their repetition, transitional expressions impair Clarity through vagueness, as using any stock expression substitutes reflex for thought. George Orwell describes the malady in "Politics and the English Language" (1946):
If you use ready-made phrases, you not only don't have to hunt about for the words; you also don't have to bother with the rhythms of your sentences since these phrases are generally so arranged as to be more or less euphonious. When you are composing in a hurry, when you are dictating to a stenographer, for instance, or making a public speech—it is natural to fall into a pretentious, Latinized style. Tags like "a consideration which we should do well to bear in mind" or "a conclusion to which all of us would readily assent" will save many a sentence from coming down with a bump. By using stale metaphors, similes, and idioms, you save much mental effort, at the cost of leaving your meaning vague, not only for your reader but for yourself.To express precise thoughts with fresh combinations of words, writers should avoid stock phrases. The same admonition applies to the subcategory transitional expressions. Other stock expressions imprecisely describe or denote the external world; transitional expressions imprecisely refer to the relations between clauses.