A sentence is a group of words you say or write down. Sentences always start with a capital letter and usually end with a period. This doesn't mean that everything that starts with a capital letter and ends with a period is a sentence, though. For instance, look at this phrase: Guzzle Brian dog late.
Not only does it not make sense, but it's also not a real sentence. This is because all sentences need two parts: a subject and a predicate.
The subject is the main person or thing the sentence is about. The predicate tells you what the subject is doing. It can also be a description of the subject. The subject and the predicate together create a complete thought.
For example, take a look at this sentence: Ned wrote me a letter. The subject here is Ned. The predicate is wrote me a letter because that's what Ned is doing. This is a simple sentence, but others can be more complicated.
For instance, some sentences can have more than one action in the predicate, like this one.
Some sentences can have more than one subject, like this one.
Here's a sentence where the predicate describes the subject.
Click the dot over the predicate in the sentence.
This is the subject of the sentence. Remember, the subject is whoever the sentence is mainly about.
This is the predicate. It tells you what the subject is doing.
Now take a look at this sentence.
What's the subject of this sentence? The subject is whoever the speaker is talking to. This kind of subject is called the invisible you. This means if you give an order or a command, the subject is always you, but you don't need to say that out loud. The person you're talking to probably knows you mean him or her.
If a sentence ends in an exclamation point, like our last example, someone is saying it with a lot of emphasis, or feeling. For instance, if you write I hate Mondays!, it shows you really hate them.
Questions are sentences too. Some questions are like sentences that have been flipped around, like this:
Question: Is Fred there?
Regular sentence: Fred is there.
Some questions also add special question words at the beginning, like this:
Where is Fred?
If you're having trouble finding the predicate in a question, you can always flip it around to make it into a regular sentence, like we did in the first two examples. You can also just take out the subject. Whatever is left will be the predicate, even if it isn't all in the same place in the sentence.
Unlike other sentences, questions don't end in periods or exclamation points. They always end in question marks.