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Bobby McFerrin demonstrates the power of the pentatonic scale, using audience participation, at the event “Notes & Neurons: In Search of the Common Chorus”.

The pentatonic scale is essentially all the black keys on a piano. These notes sound good in any order because there are no dissonant intervals between any of them.


How to Catch and Correct Run-on Sentences

A “run-on” sentence contains two (or more) independent clauses that are incorrectly joined together. (An independent clause is a word group that can stand alone as a sentence.)

To catch or to correct run-on sentences, follow these common guidelines:

  1. Join the two clauses with a comma and a coordinating conjunction*
  2. Break the run-on sentence into two separate sentences
  3. Join the clauses with a semi-colon and a conjunctive adverb** followed by a comma; however,
  4. Join the clauses with a semi-colon

*Use this mnemonic for remembering the coordinating conjunctions: FANBOYS = For, And, Nor, But, Or, Yet, So

**conjunctive adverbs include therefore, nevertheless, however, as a result, in any case, consequently, and thus


  • Body language is non-verbal everyone uses it to communicate.
  • Tom enjoys playing hockey, he plays it as much as he can.
  • Many people believe that violence on television has a negative effect on our youth, however, this topic continues to be debated.
  • Increased pollution in the environment threatens the health of millions this is an indisputable fact.


  • Body language is non-verbal, and everyone uses it to communicate. (coordinating conjunction preceded by a comma)
  • Tom enjoys playing hockey. He plays it as much as he can. (two sentences)
  • Many people believe that violence on television has a negative effect on our youth; however, this topic continues to be debated. (semi-colon + conjunctive adverb + comma)
  • Increased pollution in the environment threatens the health of millions; this is an indisputable fact. (semi-colon)



Topic Sentences

Here is another way to think about how a topic sentence can lend order to a paragraph. In the following example, the topic sentence is labeled with a “1.” Sentences that directly support the topic sentence are labeled with a “2.” Sentences that support the level 2 sentences – by providing additional detail – are designated as level “3.” By breaking the paragraph down in this manner, the relationships between the sentences – and the ideas they convey – become obvious. Using this technique to examine your own paragraphs can help you determine whether or not they are well-organized and adequately developed.

The weeks until graduation were filled with heady activities. A group of small children were to be presented in a play about buttercups and daisies and bunny rabbits. They could be heard throughout the building practicing their hops and their little songs that sounded like silver bells. The older girls (non-graduates, of course) were assigned the task of making refreshments for the night’s festivities. A tangy scent of ginger, cinnamon, nutmeg and chocolate wafted around the home economics building as the budding cooks made samples for themselves and their teachers. (From Graduation, by Maya Angelou)

Using Topic Sentences

Most paragraphs have a topic sentence that states the main point of the paragraph. Exceptions include introductory paragraphs, transitional paragraphs, and concluding paragraphs. Note also that some paragraphs are so well-structured that a reader can readily identify the topic—in other words, the topic sentence is implied rather than stated. This last technique is hard to master, so as a rule you should use a topic sentence.

Additional Examples

(Examples are from Diana Hacker. The Bedford Handbook. 5th ed. Boston: Bedford Books, 1998.)

Sample Paragraph, Topic Sentence first:

Nearly all living creatures manage some form of communication. The dance patterns of bees in their hive help to point the way to distant flower fields or announce successful foraging. Male stickleback fish regularly swim upside-down to indicate outrage in a courtship contest. Male deer and lemurs mark territorial ownership by rubbing their own body secretions on boundary stones or trees. Everyone has seen a frightened dog put his tail between his legs and run in panic. We, too, use gestures, expressions, postures, and movement to give our words point. [Italics added by Hacker.]

-Olivia Vlahos, Human Beginning (qtd. in Hacker 78).

Topic sentence introduced by transitional sentence linking it to earlier material:

But flowers are not the only source of spectacle in the wilderness. An opportunity for late color is provided by the berries of wildflowers, shrubs, and trees. Baneberry presents its tiny white flowers in spring but in late summer bursts forth with clusters of red berries. Bunchberry, a ground-cover plant, puts out red berries in the fall, and the red berries of wintergreen last from autumn well into winter. In California, the bright red, fist-sized clusters of Christmas berries can be seen growing beside highways for up to six months of the year. [Italics added by Hacker.]

-James Crockett et al., Wildflower Gardening (qtd. in Hacker 79)

Topic Sentence Last:

Tobacco chewing starts as soon as people begin stirring. Those who have fresh supplies soak the new leaves in water and add ashes from the hearth to the wad. Men, women, and children chew tobacco and all are addicted to it. Once there was a shortage of tobacco in Kaobawa’s village and I was plagued for a week by early morning visitors who requested permission to collect my cigarette butts in order to make a wad of chewing tobacco. Normally, if anyone is short of tobacco, he can request a share of someone else’s already chewed wad, or simply borrow the entire wad when its owner puts it down somewhere. Tobacco is so important to them that their word for “poverty” translates as “being without tobacco.” [Italics added by Hacker.]

-Napolean A. Chagnon, Yanomamo: The Fierce People (qtd. in Hacker 79)


Paragraph Types

¶ Writing Paragraphs

A paragraph is a group of sentences about one topic. Most paragraphs have a topic sentence that states the main point and several sentences that explain, illustrate, or prove it. The five most common paragraph structures can be seen as shapes in which the widest part is the topic sentence.

Type 1: The Upside Down Triangle

Topic Sentence first (most common)

  1. Just as the triangle tapers off to a point, the paragraph tapers from the main idea to supporting details.
  2. This is most often used in informative writing. The author states a general idea and then develops it with detailed information.


Niagara Falls has an irresistible lure for daredevils. A motley procession of foolhardy men have dared death by dancing above the chasm on a tightrope or plunging over the cataract in a barrel. Others have tried to swim the current and to shoot the rapids in boats.

Type 2: The Triangle

Topic Sentence last (second-most common)

  1. In this paragraph structure, authors present details first and then make the more general statement about the topic.
  2. Authors most often use this paragraph structure for one of three purposes:
    • To organize the details into a summary statement,
    • To present convincing details that lead readers to accept a more general claim than they might otherwise, or
    • To create suspense as they build to a climax.


Costs were low that year and output was high. There was a good man for every job and the market remained firm. There were no losses by fire. All in all, it was the best year in the company’s history.

Type 3: The Diamond

The second sentence is the topic sentence

  1. The first sentence most often serves as a transition. All other sentences develop the general idea expressed in the second sentence.
  2. Authors use this structure for one of three reasons:
    • To vary their style,
    • To provide a smooth transition from the last paragraph, or
    • To point out the relationship between ideas presented previously and those presented in this paragraph.


There are deer in abundance here. The whole area is great country for hunters and fishermen. There are bear, occasional mountain lions and coyotes. To the east the streams are full of trout and there are ducks, geese and a few pheasants.

Type 4: The Hourglass

First and last sentences are topic sentences

Authors use this paragraph structure for one of two purposes:

  • To emphasize or clarify an important idea, in which case the two topic sentences make similar statements, or
  • To present two opinions, to point out advantages and disadvantages or to show how two things are similar and/or different, in which case there is usually a signal word that alerts the reader to a change in perspective.

Example of First Purpose:

Glaciers change the surface of the earth. They grind heavily as they move slowly along, much like fresh cement creeping down a gentle slope. They dig great holes in the sides of mountains and rub away the faces of rocks. A glacier pushes masses of loose soil and rock ahead of it. The loose soil and rocks form ridges when the ice melts or stops moving. A moving glacier also makes a valley wider as it pushes down through it. The earth looks quite different after a glacier has passed by.

Example of Second Purpose:

Penicillin is one of the greatest wonder drugs. It has saved thousands of lives already and will save many more in the future. But it has no effect whatever on the bulk of the ills of man and beast. Good as penicillin is, it is certainly not a cure-all.

Type 5: The Square

There is no topic sentence

  1. All sentences contribute to the main idea which the author expects the reader to provide.
  2. This type of paragraph structure is used most often to describe, to list, or to show the sequence of events.


The range of the Mule Deer is usually east of the Sierra Nevadas. It is the largest of the North American deer, sometimes weighing almost 400 pounds. The name has been given to the species because of the long ears and the mule-like tail. Owing to its rather large antlers, it is a valuable game animal.



Infinity is bigger than you think

The scientific way to cut a cake

How to break the speed of light

Wave-particle duality—Part 2


Wave-particle duality—Part 1


What is dark matter?