Sentences are groups of words that combine to give a meaning or express a thought. They deliver ideas and facilitate learning information. Sentences in English are categorized based on different criteria, and one way to categorize them is based on the sentence structure.

There are four types of sentences:
1. Simple sentences
2. Compound sentences
3. Complex sentences
4. Compound-Complex sentences

1. The simple sentence
The simple sentence is formed of one independent clause only. It must have a subject and a verb which are the principal elements of the sentence. It must express a complete thought. It may also have an object and modifiers.
These are few examples of a simple sentence:

• Jack wrote his first novel.
• She completed her book review.
• They went to the store.
• She created her reference list.

These are quite simple and quite easy sentences to create and use.

2. The compound sentence
The compound sentence contains at least two independent clauses that have related ideas. These two independent clauses can be combined with a coordinating conjunction, a correlative conjunction, semicolon, or a conjugative adverb. Compound sentences can also be formed by combining two simple sentences that have relation with each other.
Here are a few examples of compound sentences:

• I arrived late; however, the class had not begun.
• You can either go with Jim in his car or go by bus afterwards.
• They studied APA rules for many hours, but they realized there was still much to learn.
• She completed her literature review, and she created her reference list
• We have not received your reservation; therefore, our assumption is that you will not be attending the meeting.

3. The complex sentence
A complex sentence contains at least one independent clause and at least one dependent clause. Dependent clauses can refer to the subject (who, which) the sequence/time (since, while), or the causal elements (because, if) of the independent clause. If a sentence begins with a dependent clause, note the comma after this clause. If, on the other hand, the sentence begins with an independent clause, there is not a comma separating the two clauses. The clauses express related thoughts, but one clause acts as the foundation of the sentence.
Some complex sentence examples are as follows:

• Although she completed her literature review, she still needed to work on her methods section.
• They studied APA rules for many hours as they were so interesting.
• As the bridge wasn’t properly maintained by the government, it fell down.
• Charles will be able to maintain a healthy weight if he keeps exercising.

4. The compound-complex sentence
Sentence types can also be combined. A compound-complex sentence contains at least two independent clauses and at least one dependent clause. To make a compound-complex sentence, there must be at least two independent clauses, a conjunction, and one or more dependent clauses (subordinate clauses). It is combining two sentence types together, the compound and complex sentences. In order to combine these sentences properly, attention must be made to the use of punctuation and conjunctions. If the independent and dependent clauses are combined together without using a coordinating conjunction or proper punctuation, they will form a run on sentence or a fused sentence.
The following examples show how the compound-complex sentences are formed:

• The flower girl was crying because she could not sell her flowers till evening, but when the gentleman bought the entire flower basket, she became happy.

The flower girl was crying – Independent clause
(she became happy) – Independent clause
(because she could not sell her flowers till evening) – Dependent clause
(when the gentleman bought the entire flower basket) – Dependent clause
but – Coordinating conjunction
when, because – Subordinating conjunctions

• She completed her literature review, but she still needs to work on her methods section even though she finished her methods course last semester.
• With great focus and countless resources, they studied APA rules for many hours, and they decided that writing in APA made sense because it was clear, concise, and objective.
• Although my sister was exhausted, she kept running; in fact, she got first place.

The English language has different types of sentences that are used to make communication clear and informative. It takes patience and dedication to learn everything there is to know about the types of sentences. By practice and using English sentences more often, it becomes easier to pick and choose which sentence structure that fits the communication purpose. After all, using the right sentence structure is the key to a great communication.

The different types of sentences can be used to create a topic sentence. A topic sentence essentially tells readers what the rest of the paragraph is about. All sentences after it have to give more information about the topic sentence either supporting it or giving more information or examples. You can develop a paragraph from the topic sentence. Click here to read more about the topic sentence and how to write paragraphs for university papers.