by Emily Herring, Harvard College Writing Center English Grammar and Language Tutor
#1: ARTICLES (the/a)
I found a cat. = I found any cat.
I found the cat. = I found a specific cat.
I found cats. = I found a general group of cats.
General rule: Use “a” for an unknown object; “the” for a specific, previously discussed object;
and no article for an abstract object or general concept.
I found the student’s book. = I found a book that belongs to one student.
I found the students’ book. = I found a book that belongs to many students.
I found the students’. = INCORRECT
General rule: Use ’s to indicate one person’s possession of an object and s’ to indicate a group’s possession of an object.
*The use of an apostrophe to indicate a plural is becoming widespread on social media platforms but is incorrect*
#3: SUBJECT-VERB AGREEMENT
The repairs that are occurring on the metro prevent a large portion of the population from accessing the city.
General rule: Make sure that the proper verb form (“prevent”) accompanies the subject of the sentence (“repairs”).
#4: PASSIVE VOICE
The report was written by scientists. > The scientists wrote the report. The presentation was given by the student. > The student gave the presentation.
General rule: While passive voice is not grammatically incorrect, it is better to use active voice to make your prose clearer and shorter!
#5 PAST TENSE
I lived in Boston for 3 years. > I no longer live in Boston.
I have lived in Boston for 3 years. > I still live in Boston.
General rule: Consider the time frame in which you are writing. The second example is more appropriate if you are writing in the present tense.