A noun is a person, place or thing; for example, my girlfriend (person), San Francisco (place) and skyscraper (thing).
One thing to remember about nouns is that they can function in many ways in a sentence: as a subject or direct or indirect object. Pronouns can replace nouns in sentences to avoid repetition. Common pronouns are I, you, he, she, it, we and they.
Nouns generally become plural by adding an "s" or "es" to the end; however, there are exceptions. For example, many words ending in "f" form their plural by replacing the "f" with "ves"--calf becomes calves, wharf turns into wharves, and so on. Similarly, the "y" at the end of some singular nouns also changes to an "ies"--city into cities.
Most nouns can also become possessive with the addition of an apostrophe and an "s"--the book's cover, the room's light, etc.
The part of a sentence that tells us what the subject does or is doing is called the predicate. A crucial element of the predicate are verbs and compound verbs, which put a sentence into motion.
An example of a straight, plain-old verb in a sentence: My girlfriend visits San Francisco. In this case, "visits" is the verb at work, because it tells us what "my girlfriend" is doing.
An example of a compound verb, made up of a verb and a "helping" verb like is or was: My girlfriend is visiting San Francisco. In this case, "is visiting" is the compound verb.
Simply put, an adjective modifies a noun whereas an adverb modifies a verb, adjective or phrase.
An example of an adjective in a sentence: The large truck had a problem parking in the space. In this case, the adjective is "large" because it modifies, or better describes, the truck.
An example of an adverb: The writer quickly typed the story. "Quickly" modifies typed because it tells us more about the verb: How he typed the story.
Prepositions are the links in the chain of a sentence. It usually indicates the temporal, spatial or logical relationship an object has with a subject. The most common are: at, to, in, from, about, across, after, through, beneath, with, within and without.
A conjunction also helps link two or more parts of a sentence. It can bring together words, clauses or phrases. There are coordinating and subordinate conjunctions.
A coordinating conjunction joins words, phrases and independent clauses. The most common conjunctions of this type are: and, but, or, nor, for, yet and so.
A subordinate conjunction expresses the relationship a dependent clause has with other clauses in a sentence. The most common are: because, before, although, as, how, if, when, where, whether, though, than, that and while.
Interjections help to express the emotion in a sentence. An interjection is usually followed by an exclamation mark. For example: Oh! My dog at my homework! The "oh" is the interjection. Other interjections include ah, aha, hey, ouch, uh-oh, yikes and yuk.
Now that you know the parts of speech, you have to put it all together in a complete sentence. Your sentences should have a subject and a predicate. Once again, the subject is the noun and the predicate tells what the subject is or is doing. Your sentences can make a statement, or they can ask a question. It can also make a command, which is called an imperative sentence. For example: Now you construct a sentence.