Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
Other Grammar Rules
Common Grammar Mistakes Explained
Bad grammar might distract readers from an otherwise good paper in the same way that people on the internet use typos and poor grammar to discredit arguments.
Poor grammar might also make your work more difficult to read. However, good writing may also make an otherwise bad paper appear better than it is.
Here are some longer explanations for common mistakes in scientific writing:
- Incorrectly writing units or incorrectly using hyphens
- Use hyphens with adjectives. My camera has a 24-mm lens, but the lens is 24 mm.
- Remember to put a space between the number and unit if there isn't a hyphen.
- The not-so-simple instructions were not so helpful.
- Here's more from Grammar Girl about hyphens.
- Hyphenating compound words
- Compound words can be open, closed, or hyphenated, and this can vary throughout time as English changes.
- Compound words can be traced back to Old Norse and Old English kennings, which allowed speakers to expand their limited vocabulary by creating new words formed from two or more words.
- As such, compound words might begin as open or hyphenated words and then grow into closed compound words like racehorse based on usage.
- This is one of the joys of a living language and might require the use of a dictionary.
- Using commas
- Don't just place a comma based on where you think you would take a pause
- Use a comma before a coordinating conjunction (FANBOYS = for, and, nor, but, or, yet, so) that separates two independent clauses
- We're going to the cinema, and we're going to get popcorn.
- If you have three independent clauses, this is a run-on sentence, but you can use a period or semicolon to fix it.
- We're going to the cinema, and we're going to get popcorn; but, we don't like butter.
- Use a comma after a clause or adverb introducing a sentence if it is either one word long or more than three words long. This would also occur for a sentence starting with a person's name or the words "yes" or "no."
- Today, we went to the park.
- However, tacos are superb.
- When I was following my friend home from work, she bought cotton candy.
- No, I don't have glaucoma.
- Jake, I need my coffee.
- Use a comma to separate adjectives that describe the same noun
- Timmy has a tiny, yellow truck.
- Jack and Jill went up the hill to fetch a large, brown, cylindrical object.
- Use a comma to separate a dependent clause
- Titus Andronicus, one of Shakespeare's plays, occurs in Rome.
- Titus, directed by Julie Taymor, is a movie based on the play Titus Andronicus.
- You might see someone write a similar phrase: Shakespeare's play, Titus Andronicus. However, this comma usage implies that Shakespeare only has one play and that play is Titus Andronicus.
- Here, the commas are used in the same way you might use parentheses.
- Separate items in a list with commas
- Titus Andronicus, Hamlet, and The Tempest are all Shakespearean plays.
- Christopher Marlowe wrote The Jew of Malta, Edward II and Doctor Faustus.
- The first example uses an Oxford Comma, the comma before "and," but the second example does not.
- The Oxford Comma was originally removed to save ink when publishing newspapers, though it can occasionally change the meaning of a sentence. More from Grammar Girl.
- Misusing "which" and "that"
- "That" signals a restrictive clause, and "which" signals a non-restrictive clause.
- You should always use commas before and after a dependent clause starting with "which," and you should not use commas for a clause starting with "that."
- This means that we should use "that" before a clause that is necessary for the reader's understanding of the sentence and "which" before a clause that additional additional description or detail that is not necessarily important for the reader's understanding of the sentence.
- The doctor prescribed oxandrolone, which is an anabolic steroid, to the patient.
- It isn't imperative to the sentence to know that onxadrolone is an anabolic steroid. We could remove the clause and "The doctor prescribed oxandrolone to the patient" would still make sense.
- The medication that the doctor prescribed to the patient was oxandrolone.
- "The medication was oxandrolone" doesn't make sense because the we're missing why this matters. It's important that we know what the medication was because the doctor prescribed it to the patient.
- Sometimes, you can use "that" or "which," and it often depends on the context.
- The drug that was prescribed to the patient was oxandrolone.
- The drug, which was prescribed to the patient, was oxandrolone.
- If the sentence before this one said "the patient had adverse side effects because of the drug," you could use either of the two sentences above. The first highlights the fact that the medication was prescribed. The second focuses on the name of the drug and presents the fact that it was prescribed to the patient as an additional description. You would make your choice based on the context and your message.
- Using "that" when "who" should be used
- Usage of who is similar to usage of that; however, who is used when referring to people.
- In the song "Warriors" by Imagine Dragons, they sing "we are the warriors that built this town," but they should actually sing "we are the warriors who built this town."
- You may also separate a dependent close beginning with who using commas if the clause is not essential to your sentence.
- Dean is a student at Duke who enjoys long walks on the beach.
- Dean, who enjoys long walks on the beach, is a student at Duke.
- Here's a longer explanation from Grammar Girl.