For English language learners (ELLs), the goal is to be proficient in using and understanding simple, compound, and complex sentences. While ELLs will likely be introduced to compound-complex sentences, mastery of this more advanced structure isn't typically the primary focus of B1 and B2 CEFR levels.
The progression of sentence structure mastery for these students looks like this:
A simple sentence has 1 independent clause (a subject and a verb that can stand alone as a complete thought).
Example: "The student studied." or "The student and their friends studied for the test."
A compound sentence has 2 or more independent clauses.
Independent clauses can be joined by:
A coordinating conjunction FANBOYS (for, and, nor, but, or, yet, so).
A semicolon (;).
A semicolon + conjunctive adverb (however, therefore, moreover, etc.).
Examples with semicolons:
I finished my homework; my brother started cooking dinner.
She loves to read; he prefers watching movies.
We can go to the park; or we can stay home.
With conjunctive adverbs:
I studied hard; however, I still found the test difficult.
He was tired; therefore, he went to bed early.
A complex sentence has 1 independent clause with 1 or more dependent clause.
Dependent clauses often begin with subordinating conjunctions (e.g., because, since, although, when, if, while, before, until, unless) or relative pronouns (e.g., who, which, that).
Example: "Because the student studied diligently, they felt prepared for the test."
A compound-complex sentence has 2 or more independent clauses and 1 or more dependent clause.
In other words, it’s a mix of a compound sentence (two or more independent clauses joined by a coordinating conjunction like and, but, or) and a complex sentence (an independent clause plus at least one dependent clause).
"I enjoy hiking because it relaxes me, and my brother prefers swimming."
Independent clause 1: I enjoy hiking
Dependent clause: because it relaxes me
Independent clause 2: my brother prefers swimming
This makes it a compound-complex sentence because it has 2 independents + 1 dependent.
While the vast majority of grammar errors are found within the structure of a sentence, there are several types of errors that can occur outside of a complete sentence. Here are some examples:
Punctuation errors: These can happen anywhere, even in a single word or phrase. Think of a comma splice, a misplaced apostrophe in a possessive noun (e.g., "the dog's," versus "the dogs'"), or a run-on sentence. These are often considered sentence-level errors, but they are specifically related to punctuation, not just word order.
Word-level errors: These can include spelling mistakes (which are often considered a separate category, but are sometimes grouped under grammar), incorrect word choice (e.g., using "affect" instead of "effect"), or using a word in the wrong form (e.g., "their" vs. "there").
Capitalization errors: This can happen with a single word or at the beginning of a heading or title.
Fragment errors: This is an incomplete thought that is punctuated as a complete sentence. While it is related to the idea of a sentence, the error is in the fragment's lack of a full subject or verb.
While sentence structure is the most common place to find grammar errors, they can also occur at the word, phrase, and punctuation level.