You should come to a freshman English class with a basic understanding of grammar. If you have forgotten basic sentence structures, you should review the parts of speech, which are nouns, pronouns, verbs, adjectives, adverbs, articles, prepositions, conjunctions, and interjections. Articles (a, an, the) appear in front of nouns, and interjections (oh my!) usually stand alone. The other parts of speech, however, come in several varieties and may appear in different places in a sentence. To be certain what part of speech a word is, you should not only look at the actual word, but also at its meaning, position, and use in a sentence.