<2.parstr> Paragraph Structure Paragraphs should normally move from the general to the specific. Often, as in the example below, they move from a transitional sentence to a topic sentence, followed by a series of supporting sentences: (l) transition sentence: links the paragraph to what has just been said (2) topic sentence: provides overview of paragraph (3) supporting sentences: elaborate the topic of the paragraph EXAMPLE __________ (1)-> We have seen in the previous paragraph that heat transfer through a temperature difference is an irreversible process. (2)-> How, then, can we have a reversible heat-transfer process? (3)-> Since heat is defined as energy that is transfered because of a temperature difference, a heat-transfer process approaches a reversible process as the temperature approaches zero. Hence, we define a reversible heat-transfer process as one in which the heat is transferred through an infinitesimal temperature difference. We realize, of course, that to transfer a finite amount of heat through an infinitely small temperature difference would require an infinite amount of time or an infinite area. It follows that all actual heat-transfer processes take place through a finite temperature difference and are, hence, irreversible. _________ The example above is a relatively common structure of a paragraph. But there are other possiblities. Some paragraphs begin with the topic sentence, and the transitional note is secured with the repetition of a term or subject in the previous paragraph.