STEP 1: DEFINITION

All complete sentences in English must have a subject and a verb. These sentences, called clauses, can be dependent or independent. They are divided into four types: simple, complex, compound, and compound-complex.

1. Simple sentences have a subject (or a compound subject) and at least one verb.

Paul reads well.
John runs.
Mary smiles.

2. Complex sentences contain a dependent and an independent clause. Dependent clauses usually begin with conjunctions such as if, even though, when, and while.

If he gets here soon, we can leave.
Even though he is poor, he has a positive outlook on life.
While we're waiting for class to begin, we should study our notes.

3. Compound sentences join two independent clauses. They can be united by semi-colons, or comma + conjunction (and, or, nor, so, for, but, yet).

You can leave at 5:00 pm; however, you must be on time.
Kylee wants to see a movie, but Sara wants to see a play.

4. Compound-complex sentences contain both a complete sentence and a dependent and an independent clause.

Although I knew he was going to arrive on time, my friends thought that he would be late, so they refused to meet him at the airport.
She doesn't want to leave the class that she most enjoys, but she has to go because she is ill.

5. Phrases (groups of words without subjects and verbs) and dependent clauses that are incorrectly punctuated are called fragments.

When I get a job and earn some money.
According to the research that the scientist has done.

6. Incorrect punctuation also creates errors such as comma splices and run-on sentences.

Traveling around the country is interesting, it can offer new insights.
People who enjoy traveling can sign up for tours however they might prefer
seeing the sights on their own.

Problems with English sentence structure often arise when authors use incorrect punctuation, omit or include unnecessary conjunctions, or write incomplete sentences (fragments).

Incorrect: Although he wants to succeed, but he has many obstacles to overcome.

Correct: Although he wants to succeed, he has many obstacles to overcome.

Incorrect: Garrett can attend the party, his wife will not be there.

Correct: Garrett can attend the party, but his wife will not be there.

Incorrect: Even grandmothers, nieces, and nephews.

Correct: Even grandmothers, nieces, and nephews are invited.

Incorrect: Some tourists apply for visas however others just come to visit.

Correct: Some tourists apply for visas, however others just come to visit.

STEP 2: PRACTICE EXERCISES

Practice 1 - Recognizing sentence structure errors in sentences
Practice 2 - Recognizing sentence structure in paragraphs

STEP 3: LEARNING MORE

For more information on sentence structure, follow these links:
http://www.uottawa.ca/academic/arts/writcent/hypergrammar/sntstrct.html
http://www.uottawa.ca/academic/arts/writcent/hypergrammar/rvsntstr.html
http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/adj.htm