Any English teacher will tell you that knowing the parts of speech is absolutely vital to writing good sentences. The parts of speech are the building blocks of sentences; it is impossible to write grammatically correct sentences without knowing at least some of the them. Knowing all of the parts of speech can help advance your writing skills and prevent them from plateauing.

Grammar as Patterns

Humans recognize patterns. Grammar is essentially a system of patterns applied to words that organizes them in a particular way. Without a grammatical system, we wouldn't be able to communicate with one another. Through reading, speaking and writing, we internalize grammatical patterns until they become so familiar that any deviation from them, such as saying, for example, "she don't," instead of "she doesn't," immediately sounds wrong to us. Indeed, such obvious errors in speaking signal that a person's native language is not English. But even native English speakers' grammar is not always perfect. English speakers can brush up on their grammar, too, including the basics: the parts of speech.

Error Identification

Fixing grammar problems in your writing is extremely difficult without knowing the eight parts of speech. Sometimes you may encounter a sentence in your writing that doesn't sound right, but you can't explain why or determine how to improve it. Other times a teacher may circle a sentence in your writing that needs fixing, but you don't understand what's wrong with it. In both cases having a firm grasp on the parts of speech and their functions can help you correct the sentence. Grammatical problems such as subject-verb disagreement, pronoun-antecedent disagreement, run-on sentences, sentence fragments and comma splices all require knowledge of certain parts of speech to fix. Furthermore, if you aren't familiar with the parts of speech, assuring yourself that a sentence you have written is correct is difficult.

Sentence Variation

Effective writing contains sentences of varying patterns and lengths. The English language contains only four basic sentence patterns, which are, ascending in complexity, simple, compound, complex and compound-complex. Each one contains a different number of independent and dependent clauses. You can identify the four different sentence patterns by the parts of speech they contain. Writing that utilizes a variety of sentence structures reads more interestingly, whereas too many simple sentences in a row sounds monotonous.

Parallelism

Parallelism problems result in awkward sentence structure, and this common writing malady afflicts many people without their realizing it. A person who can master parallel sentences can set himself apart from other writers. Parallel problems are virtually impossible to solve without knowing the parts of speech. The sentence "Love and being married go together" sounds awkward because the two things compared are not in parallel grammatical form. "Love" is a noun, while "being" is a gerund and "married" is an adjective. The sentence sounds smoother reworded as "Love and marriage go together."