A loose sentence is an English grammatical term referring to a sentence which contains a main statement followed by one or more subordinate clauses. The subordinate clauses may directly modify the main statement or add extra details that expand on its meaning and intent. Writers and speakers can use a loose sentence as a way of breaking up the simplicity of the basic subject-verb format of a simple sentence. Loose sentences are related to but differ somewhat from periodic sentences, which have the subordinate clauses interrupting the main thrust of the sentence.
The best writers have the ability to keep readers interested by varying their style throughout their prose. They can do this with the language that they use or the tone of their content, or they can use different grammatical techniques to keep readers constantly surprised and engaged. Varying the sentence structures that are available to them is one effective manner of doing this. One of the techniques at writers' disposal is the loose sentence, which takes a basic subject-verb construction and builds layers on top of it.
It is important to understand that the loose sentence always has some main statement at the beginning that can stand on its own as a sentence. For example, the basic thrust of one such sentence might be "The birds flew away." To expand upon the simplicity of this sentence, the writer might add, "The birds flew away, since they knew the winter was fast approaching." The writer could then go even further by saying, "The birds flew away, since they knew that winter was fast approaching, threatening to freeze their fine feathers."
As that example shows, a loose sentence can add many details to the main idea at the start of the sentence. By contrast, a periodic sentence also adds details, but it does so by interrupting the flow of that main idea. Changing the previous example into a periodic sentence might yield the following: "The birds, knowing that winter was fast approaching, threatening to freeze their fine feathers, flew away."
Exploiting the slight difference between a loose sentence and a periodic sentence can give a writer several options on how to approach complex sentences. Loose sentences can have a powerful effect as more and more phrases are piled onto the main idea, allowing for a writer to really hammer home his or her point. By contrast, a periodic sentence can keep the reader in suspense by keeping the completion of the main thought at bay for several phrases, before it finally arrives in an impactful conclusion.