Item 01
The house _____ is on the corner is blue.
Reveal answer
Correct answer
- The house that is on the corner is blue.
Incorrect answer
- (b) which
Grammar Concepts #12
That vs Which: Understanding Essential and Non-Essential Information
This rebuilt lesson keeps the original concept image, tightens the structure, and turns the explanation into a clearer self-study guide.
Core Idea
When learning English, it’s important to understand how to use the words that and which correctly. These words are used to introduce clauses that describe nouns, but their usage depends on whether the information in the clause is essential or non-essential to the meaning of the sentence.
Key Points
Essential Information: Using “That”
When the information included is essential to the meaning of a sentence, we use “that” without commas. Essential information provides details that are necessary to understand the noun it describes. If we remove the essential clause, the sentence loses important meaning.
Examples:
- The shape that is red is called a “cube”.
- Here, “that is red” is essential because it specifies which shape is being referred to.
- The tool that is completely silver is called a “wrench”.
- “That is completely silver” is essential to identify the specific tool.
- The animal that has big ears is an elephant.
- “That has big ears” is essential to specify which animal.
More examples:
- The book that has a blue cover is mine.
- The car that is parked outside belongs to John.
- The student that studies the most often gets the best grades.
Non-Essential Information: Using “Which”
When the information included is not essential to the meaning of a sentence, we use “which” with commas. Non-essential information provides extra details that can be removed without changing the basic meaning of the sentence.
Examples:
- The shape, which is red, is a cube.
- “Which is red” adds extra information about the shape but is not necessary to identify it as a cube.
- The tool, which is completely silver, is a wrench.
- “Which is completely silver” gives additional information but is not essential to know it’s a wrench.
- The animal, which has a hump, is a camel.
- “Which has a hump” provides extra detail about the animal but isn’t necessary to identify it as a camel.
More examples:
- The book, which has a blue cover, is mine.
- The car, which is parked outside, belongs to John.
- The student, who studies the most, often gets the best grades.
Special Note: Using “Who”
If the subject is a person, the word “who” is used in both cases. However, commas are still used when the information is non-essential.
Examples:
- The girl who won the race is my sister. (Essential)
- “Who won the race” is essential to identify which girl.
- My sister, who won the race, is very fast. (Non-Essential)
- “Who won the race” adds extra information about my sister but is not necessary for the main point.
More examples:
- The teacher who assigned the homework is very strict. (Essential)
- Mr. Johnson, who assigned the homework, is very strict. (Non-Essential)
- The man who lives next door is a doctor. (Essential)
- Dr. Smith, who lives next door, is very kind. (Non-Essential)
Summary
- Use “that” for essential information without commas.
- Use “which” for non-essential information with commas.
- Use “who” for people, following the same rules for essential and non-essential information.
Understanding the difference between essential and non-essential information will help you use that and which correctly, making your English more precise and clear.
Practice Check
Answer the quiz questions below with responses consistent with the grammar concepts taught on the left.
Practice Check
Item 02
The car, _____ is red, is very fast.
Reveal answer
Correct answer
- The car, which is red, is very fast.
Incorrect answer
- (a) that
Item 03
The book _____ I borrowed was excellent.
Reveal answer
Correct answer
- The book that I borrowed was excellent.
Incorrect answer
- (b) which
Item 04
My phone, _____ is very old, still works fine.
Reveal answer
Correct answer
- My phone, which is very old, still works fine.
Incorrect answer
- (a) that
Item 05
The movie _____ we watched last night was scary.
Reveal answer
Correct answer
- The movie that we watched last night was scary.
Incorrect answer
- (b) which
Item 06
The flowers, _____ are on the table, are for you.
Reveal answer
Correct answer
- The flowers, which are on the table, are for you.
Incorrect answer
- (a) that
Item 07
The student _____ studies the hardest usually succeeds.
Reveal answer
Correct answer
- The student that studies the hardest usually succeeds.
Incorrect answer
- (b) which
Item 08
My computer, _____ is very fast, helps me work efficiently.
Reveal answer
Correct answer
- My computer, which is very fast, helps me work efficiently.
Incorrect answer
- (a) that
Item 09
The song _____ she sang was beautiful.
Reveal answer
Correct answer
- The song that she sang was beautiful.
Incorrect answer
- (b) which
Item 10
The cake, _____ was chocolate, was delicious.
Reveal answer
Correct answer
- The cake, which was chocolate, was delicious.
Incorrect answer
- (a) that
Item 11
The book _____ has a red cover is mine.
Reveal answer
Correct answer
- The book that has a red cover is mine.
Incorrect answer
- (b) which
Item 12
The car, _____ is parked outside, is my sister’s.
Reveal answer
Correct answer
- The car, which is parked outside, is my sister’s.
Incorrect answer
- (a) that
Item 13
The dog _____ barked all night kept us awake.
Reveal answer
Correct answer
- The dog that barked all night kept us awake.
Incorrect answer
- (b) which
Item 14
My brother, _____ lives in New York, is visiting us.
Reveal answer
Correct answer
- My brother, who lives in New York, is visiting us.
Incorrect answers
- (a) that
- (b) which
Item 15
The bike _____ I ride is very old.
Reveal answer
Correct answer
- The bike that I ride is very old.
Incorrect answer
- (b) which
Item 16
The movie, _____ stars my favorite actor, is a hit.
Reveal answer
Correct answer
- The movie, which stars my favorite actor, is a hit.
Incorrect answer
- (a) that
Item 17
The building _____ collapsed was very old.
Reveal answer
Correct answer
- The building that collapsed was very old.
Incorrect answer
- (b) which
Item 18
The painting, _____ was stolen, is very valuable.
Reveal answer
Correct answer
- The painting, which was stolen, is very valuable.
Incorrect answer
- (a) that
Item 19
The restaurant _____ we went to was expensive.
Reveal answer
Correct answer
- The restaurant that we went to was expensive.
Incorrect answer
- (b) which
Item 20
The shoes, _____ are black, are very comfortable.
Reveal answer
Correct answer
- The shoes, which are black, are very comfortable.
Incorrect answer
- (a) that
Item 21
The film _____ we watched last night was interesting.
Reveal answer
Correct answer
- The film that we watched last night was interesting.
Incorrect answer
- (b) which
Item 22
The tree, _____ is very old, provides a lot of shade.
Reveal answer
Correct answer
- The tree, which is very old, provides a lot of shade.
Incorrect answer
- (a) that
Item 23
The cat _____ caught the mouse is very clever.
Reveal answer
Correct answer
- The cat that caught the mouse is very clever.
Incorrect answer
- (b) which
Item 24
The teacher, _____ assigned the homework, is very strict.
Reveal answer
Correct answer
- The teacher, who assigned the homework, is very strict.
Incorrect answers
- (a) that
- (b) which