Coherence is a chracteristic of good writing, its ability to flow smoothly and understandably for readers. Transitional techniques, covered here in this chapter, are a major contributor. Of course, if a document has organizational problems, no amount of ingenious transitional techniques can help create coherence. Sequencing and outlining are covered in a separate chapter.

This chapter contains a lot of information, but it boils down to these two key ideas:

These ideas are discussed in the following.

Topic Strings for Coherence

Coherence can achieved by simply rearranging the occurence of keywords in paragraphs or sections. Look for a keyword that conspicuously occurs multiple times. Think of the occurrences of those keywords as a topic string. There seem to be two basic types of topic strings: continuous topic strings and shifting topic strings.

Continuous Topic Strings

Here's an example of a continuous topic string, one in which the topic word is roughly the same each occurrence:

Mars is the fourth planet from the Sun in our solar system and is named after Mars, the Roman god of war. Mars is also known as the "Red Planet" due to its reddish appearance when seen from Earth. The prefix areo-, from the Greek god of war, Ares, refers to Mars in the same way geo- refers to Earth. Mars has two moons, Phobos and Deimos, which are small and oddly-shaped.

In this example, the topic string involves the repetition of Mars. Four different things are said about Mars: its location and name; its reddish appearance; its prefix name; its moons. When you start analyzing paragraphs for topic strings, you can more readily see minor organizational variations: in this example, the two sentences that discuss the planet's name could be put together rather than interrupted by the reddish-appearance sentence. Static topic strings like this one are instances of the coordinate paragraph structure: four same-level things are stated about Mars. This paragraph could be diagrammed as follows:

Sentence beginning Sentence ending
Mars location, name
Mars name, reddish appearance
name, prefixes Mars
Mars moons

This diagram identifies the topics at the beginning of the sentences, which are in all but one case Mars. The diagram also identifies the topics at the end of the sentences, which again in all but one case are various aspects of Mars. Is sentence 3 flawed because Mars occurs at the end? No, not really, because the preceding sentences have firmly established Mars as the topic and because beginning every sentence with Mars might create a distracting monotony.

Here's another example of a continuous topic string, but one that doesn't look continuous at first:

Barely stifled yawns greeted the electronics novelty that was introduced to the public in mid-1948. "A device called a transistor, which has several applications in radio where a vacuum tube ordinarily is employed, was demonstrated for the first time yesterday at Bell Telephone Laboratories," noted an obviously unimpressed New York Times reporter on page 46 of the day's issue. To be sure, the gadget had plusses. Not only could the transistor amplify electric current like a vacuum tube, it also used little power, didn't need to warm up, and was compact——a thimble-sized cylinder with a couple of protruding wires. But because its main ingredient was an expensive, hard-to-handle element called germanium, the transistor seemed likely to remain a laboratory curiosity.

In this example, the focus is obviously transistor, but notice the synonyms used to refer to this topic:

Sentence beginning Sentence ending
electronics novelty date
transistor lack of interest, usefulness
gadget plusses
transistor positive features
germanium problem
or
transistor
transistor
or
lab curiosity

Is this good writing, or bad? The excerpt seems to violate the rule about calling a object or an action by the same name. But for some reason this variation seems appropriate—probably because is creates a little suspense, which is relieved when the well-known term transistor is unveiled.

If you had problems analyzing the topics in the preceding example, you are not alone. The reason is the lack of precision in this method of analysis. All clauses—not just independent ones but dependent ones as well—have a beginning and ending topic. In dependent clauses, the beginning topic is not always directly expressed. However, finetuning this analysis to include all clauses may reduce its usefulness as a tool for ordinary writers. But here's an effort:

Clause beginning Clause ending
yawns electronics novelty
that (electronics novelty) introduction date
which (transistor) vaccuum-tube-like applications
transistor demonstration location, date
gadget plusses
transistor vaccuum-tube-like function
it (transistor) positive features
its germanium problem
transistor laboratory curiosity

Now you can see that transistor, some synonym for it, or some pronoun such as that, which, or it begins every clause in this excerpt, not just every sentence. Notice some other details about this analytic technique:

Does this more precise method of analyzing topic strings in paragraphs work? Or does its fussy exactitude damage its usefulness as a tool for analyzing and improving paragraphs? Let's vote.

This next example can be analyzed in two ways:

A solar cell (or a "photovoltaic" cell) is a semiconductor device that converts photons from the sun (solar light) into electricity. To achieve this conversion, the device needs to fulfill only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaics.

Obviously, the focus is solar cell, but each sentence focuses on the conversion process it achieves:

A solar cell (or a "photovoltaic" cell) is a semiconductor device that converts photons from the sun (solar light) into electricity. To achieve this conversion, the device needs to fulfill only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaics.

In this second analysis, the initial instance of solar cell is highlighted because it begins the discussion. The focus of the discussion then shifts to conversion. It's useless to argue whether the continuous topic string here is solar cell or conversion. It is useful, however, that the process of analyzing paragraphs for topic strings enables you to see these two patterns.

Shifting Topic Strings

As the final example in the preceding section hints, the topics in a topic string sometimes vary; they don't just repeat the same old topic. In this case, you have a variable or shifting topic string. Here's that Mars example again, but in its original version:

Mars is the fourth planet from the Sun in our solar system and is named after Mars, the Roman god of war. Mars is also known as the "Red Planet" due to its reddish appearance when seen from Earth. The red/orange appearance of Mars' surface is caused by iron oxide. The prefix areo-, from the Greek god of war, Ares, refers to Mars in the same way geo- refers to Earth. Mars has two moons, Phobos and Deimos, which are small and oddly-shaped.

In this example, the topic string still involves the repetition of Mars. This time, five different things are said about Mars: its location and name; its reddish appearance; the reason for the reddish appearance; its prefix name; its moons. The second occurrence of appearance creates a single disruption in the essentially continuous topic string.

Look closely at what's happening in this second Mars example: sentence 2 starts with the topic Mars then ends with the topic reddish appearance; sentence 3 starts with reddish appearance and then ends with a causal explanation for that reddish appearance, signaled by the words is caused by. This pattern is called by Joseph M. Williams and others the old-to-new pattern.

Sentence 2 Sentence 3
Mars > reddish appearance red/orange appearance > Mars

This example shifts for one sentence to a new topic then back to the old topic. Here is another example in which the old-to-new shift is not so temporary:

The surface of Mars is thought to be primarily composed of basalt, based upon the Martian meteorite collection and orbital observations. There is some evidence that a portion of the Martian surface might be more silica-rich than typical basalt, perhaps similar to andesitic stones on Earth, though these observations may also be explained by silica glass. Much of the surface is deeply covered by iron oxide dust as fine as talcum powder. There is conclusive evidence that on the surface of Mars liquid water existed at one time. Key discoveries leading to this conclusion include the detection of various minerals such as hematite and goethite which usually only form in the presence of water.

At first, you may have throught, "Oh, yes. Another paragraph about Mars." However, if you look more closely, you see that surface occurs in the first three sentences but not in the last, where water is the topic. In the pivotal sentence 4, the focus shifts from surface to water. This is another old-to-new topic shift. In sentence 4, the old topic, surface, occurs appropriately at the beginning of the sentence; and the new topic, water, occurs appropriately toward the end of sentence 4. Scholars of writing technique advocate starting a sentence with familiar information (topics that have already been introduced) and then ending sentences with new information (new topics). Otherwise, starting each sentence with a new topic puts a cognitive strain on readers, making them work much harder, harder than necessary, to understand the discussion.

However, the old-to-new shift can go on multiple times. When that happens, the writer is going deeper and deeper into the overall topic of the paragraph. In terms of paragraph coordination and subordination, the writer is creating a highly subordinate structure with a shifting topic string. A continuous topic string, on the other hand, is a highly coordinate structure. Here's an example:

1 The most important part of a solar heating system is the solar collector whose main function is to heat water to be used in space heating.
2 There are various types of collectors.
3 However, the most common type is the flat-plate collector and is the focus of the following discussion.
4 A flat-plate collector consists of a box-shaped black plate absorber covered by one or more transparent layers of glass or plastic with the sides and the bottom of the box insulated.
5 These layers of glass or plastic have an intervening air space that produces the heat-trapping effect.
6 Water is heated as it circulates through or below the absorber component, which is heated by solar radiation.

Clause beginning Clause ending
1 solar heating system solar collector
2 types collectors
3 type flat-plate collector
4 flat-plate collector layers
5 layers heat-trapping effect
6 (water) heated (circulation)

The topic string in this paragraph is predominately shifting:

  1. The starting topic in sentence 1 is solar heating system, and the ending topic is solar collector.
  2. solar collector becomes the old topic in sentence 2 (whose structure forces the new topic types to start the sentence).
  3. Sentence 3 states the old topic from sentence 2, type. The new topic flat-plate collector ends the sentence.
  4. Sentence 4 returns to the old-to-new pattern with an old topic, flat-plate collector, beginning the sentence, and the new topic, layers, ending the sentence.
  5. This textbook-style pattern continues in sentence 5, where layers, now the old topic, starts the sentence; and heat-trapping effect, the new topic, ends the sentence.
  6. In the final sentence, however, this perfect pattern is distorted a bit: water, a new topic, starts the sentence; and heats, echoing the old topic, follows.

Do these variations and distortions of the perfect old-to-new pattern cause any coherence problems? Probably not: enough sentences follow the pattern and the repetition of key topic words is strong enough to create what seems a reasonably coherent discussion. But let's vote!

Topic Strings and Paragraph Analysis

Analyzing topic strings in paragraphs can be a useful tool in determining why paragraphs might be difficult to read, follow, and understand. This analysis enables you to gauge how much mental work you are making your readers do. Read this discussion first to see if you understand it, or if it takes you a couple of readings to understand it:

1 The development of the transistor goes back to the nineteenth century.

2 Germanium and silicon, along with a number of other crystalline materials, are semiconductors, so-called because they neither conduct electricity well, like most metals, nor block it effectively, as do insulators such as glass or rubber.

3 Back in 1874 a German scientist named Ferdinand Braun identified a surprising trait of these on-the-fence substances: Current tends to flow through a semiconductor crystal in only one direction.

4 This phenomenon, called rectification, soon proved valuable in wireless telegraphy, the first form of radio communication.

5 When electromagnetic radio waves traveling through the atmosphere strike an aerial, they generate an alternating (two-way) electric current.

6 However, earphones or a speaker must be powered by direct (one-way) current.

7 Methods for making the conversion, or rectification, in wireless receivers existed in the closing years of the 19th century, but they were crude.

8 In 1899 Braun patented a superior detector consisting of a semiconductor crystal touched by a single metal wire, affectionately called a "cat's whisker."

9 His device was popular with radio hobbyists for decades, but it was erratic and required much trial-and-error adjustment.

Most people would find this excerpt hard going. It gives your brain a workout—which may be a good thing, after all but risky. However, if you believe that readers deserve text that can be undserstood as effortlessly as possible, this excerpt needs some work. Here's the analysis:

  1. Nothing connects sentence 1 and 2: you have to guess or eventually realize that semiconductors are the essential ingredient of transistors.
  2. However, there is a connection between sentence 2 and 3: these on-the-fence substances refers back to semiconductors although you have to do some brain work to make that connection.
  3. Sentences 4 is nicely connected to sentence 3 by the words This phenomenon.
  4. Sentence 5's connection to the preceding is hard to determine: you have to make the connection between electromagnetic radio waves traveling through the atmosphere (and aerial) to wireless telegraphy in sentence 4. Alternatively, you could say that radio occurs in the new position at the end of sentence 4 and in the old position in sentence 5. But does it work well as a old-to-new connector?
  5. Sentence 6 is helped by the transition word however and by the contrastive (one-way) which mirrors (two-way) in the sentence 5. But for general readers, the connections to the preceding may still be mysterious.
  6. The connections from sentence 7 to the preceding may also be difficult. We heard about rectification and wireless is sentence 4. It's as though the writer has thrown out three barely related statements and we are waiting for the writer to tie it all together.
  7. Sentence 8 continues the mystery: yes, we've heard about Braun and semiconductors, but there are lots of new topics here and no clues as to the relationship of this sentence to has preceded.
  8. The final sentence wanders off into a side issue, and general readers are left to put all these ideas together by themselves. Thanks, writer.

Transitional Words and Phrases

As mentioned way up there at the beginning of this chapter, there is another category of transitional devices—transitional words and phrases. These show how a preceding chunk of information is logically related to a current or upcoming chunk of information—they look backward and forward at the same time. For example:

It may be 3 a.m., but I'm not sleepy a bit.

In this example, the transitional word "but" sets up a contrast between the topic of the first chunk of information (the lateness of the time) and the second chunk (my lack of sleepiness). The logic is contrastive in this case, but there are other kinds of logic. For example:

My Peugeot has almost 112,000 miles on it. It still runs great!

In this example, the transitional word is "it," a simple pronoun. Here, the logic is additive, I'm simply adding one related thought onto another. These examples are obviously stupidly simplistic—but when you get into a complex technical topic and the chunks are whole paragraphs of information, transitions really begin to matter.


Revising problems with transitions. The problem version reads like a series of disconnected statements floating in space. The revised version adds transitional devices to pull the statements together in a "coherent," flowing discussion.

  • Basic transitional words and phrases. People who have studied the way communication, in particular, writing, works have identified these kinds of basic logic that knit ideas together. They are so obvious that they really need not clutter up this chapter at this point. But go take a look at the basic transitional words and phrases.
  • It takes a surprising amount of brain power to construct a transition: you must know the topic of the preceding chunk of information, the topic of the current or upcoming one, the logic that connects them. Then, with that in mind, you must pick out the transitional device that you think will best guide the reader across that juncture between the two chunks of information. Scholars have identified a half-dozen or so kinds of transitional devices (but it seems like there ought to be more...):

    Dynamic transitional words and phrases. Another category of transitional words and phrases words that are echoed from a preceding section or that forecast keywords in the next section.

    • Pronouns—Pronouns like it, this, or that—occuring alone without a following noun—are the weakest of transitional devices. In the following examples, notice how effective they can be when combined with a clarifying noun.
    • Summary transitions—At key points in writing, you'll see a phrase, sometimes accompanied by a pronoun, that summarizes the preceding discussion. In the same sentence, a statement will be made about that summary phrase—typically this phrase will kick off the upcoming discussion, and do so in a way that the reader sees the connection between what came before and what is coming next. In this example this mismatch summarizes the idea expressed in the preceding discussion:


      Summary transitions. Notice how the underlined summary transition pulls together the idea expressed in the preceding discussion.


      Summary transitions. Notice how the underlined summary transition pulls together the idea expressed in the preceding discussion.
    • Review-preview transitions—The most powerful transitional device you can use is the type that summarizes the topic of the preceding chunk of information into a short phrase, does the same thing for the upcoming chunk of information, finds the appropriate transitional word, and then throws all these elements together into a sentence or two. You'd use this device at those major bridge points in reports, between large chunks of information—for example, between one 7-page section and a 9-page section that follows it.

      Review-preview transition. Notice how the topic of the preceding section Coring and core nanalysis techniques is echoed; then transitional material However, a much faster and less expensive... introduces the topic for this next section wire-line logging analysis. (From a report written in 1983.)