We've talked about how every clause is a notion, i.e., the brain noticing something or interpreting what it's noticed. One or several clauses for a complete sentence, just as one or more notions form a complete thought. But how do we know when a sentence should end?
Sentences should be a single thought (same topic, same purpose).
Here, topic is not interchangeable with subject, as sentences can have different grammatical subjects:
I can't believe that Annie has the nerve to complain about going to Barcelona for spring break when she knows I'm going to be stuck camping in Idaho. Idaho!
There are four clauses and four different subjects: I, Annie, she, and I (in I'm). But there is just one topic: the speaker is mad that Annie is complaining about her upcoming trip when it'll be heavenly compared to the speaker's upcoming trip. Here's another example of multiple subjects, one topic:
Marnie told me that she entered Biscuit into the town dog show, but I'm still not sure that my dog Smuckers should enter the competition too.
Marnie, she, I, and dog Smuckers are the subjects of the four clauses in this sentence, but the sentence is only about one topic: the dog show and which dogs will (or won't) enter. Writers need to end a sentence before the topic changes and their thoughts start to run together.
Sentences should be a single thought (same topic, same purpose).
Here, topic is not interchangeable with subject, as sentences can have different grammatical subjects:
I can't believe that Annie has the nerve to complain about going to Barcelona for spring break when she knows I'm going to be stuck camping in Idaho. Idaho!
There are four clauses and four different subjects: I, Annie, she, and I (in I'm). But there is just one topic: the speaker is mad that Annie is complaining about her upcoming trip when it'll be heavenly compared to the speaker's upcoming trip. Here's another example of multiple subjects, one topic:
Marnie told me that she entered Biscuit into the town dog show, but I'm still not sure that my dog Smuckers should enter the competition too.
Marnie, she, I, and dog Smuckers are the subjects of the four clauses in this sentence, but the sentence is only about one topic: the dog show and which dogs will (or won't) enter. Writers need to end a sentence before the topic changes and their thoughts start to run together.
END PUNCTUATION
Periods.
Periods most commonly mark the end of a declarative or imperative sentence. They also follow at the end of indirect questions (Dirty Harry asked the punk if he was feeling lucky.) Periods are also used at the end of an abbreviated word to show that it is abbreviated (Dr., Mrs., Blvd., etc). Periods also follow letters in acronyms when those letters are pronounced separately (A.A.R.P., W.B.), but not when the acronym is said as its own word (NASA, PETA).
Question marks? And exclamation points!
Question marks indicate the end of a direct question (How far is the town?). Exclamation points indicate the end of an exclamatory interjection (Ow!) or sentence (He killed her in my bed!). In formal writing, these marks are always singular (so stop writing "It was a blast!!!"). If a direct question is exclamatory, use an interroburst, which is an exclamation point superimposed over a question mark.
Ellipses . . .
The final way to end a sentence is to use ellipses, or a series of three spaced periods. This indicates that a thought or sentence is trailing off (I couldn't quite remember . . . .) or when words are omitted in a quotation ("We all survived . . . survived despite the cost.") Remember that an ellipsis consists of three periods except when ending a sentence, where there are three periods for the ellipsis and one more to end the sentence.