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My bicycle which has a bright blue frame was stolen last week.
ND (My bicycle, which has a bright blue frame, was stolen last week.)
Why? "My bicycle" is specific. The color is extra information. Needs commas.
This museum which was built in the 19th century has a beautiful facade.
ND (This museum, which was built in the 19th century, has a beautiful facade.)
Why? "This museum" is specific. Its construction date is non-essential. Needs commas.
The theory of relativity which was developed by Einstein changed modern physics.
ND (The theory of relativity, which was developed by Einstein, changed modern physics.)
Why? "The theory of relativity" is a specific, identified theory. The clause adds a non-essential fact. Needs commas.
The Amazon River which is in South America is the largest river
ND (The Amazon River, which is in South America, is the largest river.)
Why? "The Amazon River" is a specific, identified river. The location is an extra fact. Needs commas.
The Eiffel Tower which was completed in 1889 is made of iron.
ND (The Eiffel Tower, which was completed in 1889, is made of iron.)
Why? "The Eiffel Tower" is a unique, identified monument. The completion date is an extra fact. Needs commas.
Everest which is the highest mountain in the world is in the Himalayas.
ND (Everest, which is the highest mountain in the world, is in the Himalayas.)
Why? "Everest" is a unique, identified mountain. The clause is an extra fact. Needs commas.
The author who wrote this series will give a talk at the library.
D (The author who wrote this series will give a talk at the library.)
Why? "Who wrote this series" identifies which author. No commas.
The woman whose dog ran away is putting up posters.
D (The woman whose dog ran away is putting up posters.)
Why? "Whose dog ran away" identifies which woman. No commas.
The cake that my mother baked for my birthday was delicious.
D (The cake that my mother baked for my birthday was delicious.)
Why? "That my mother baked" tells us which specific cake. No commas.
The book that I'm reading right now is about space exploration.
D (The book that I'm reading right now is about space exploration.)
Why? "That I'm reading right now" tells us which specific book. No commas.
The chef who cooked our meal trained in Italy.
D (The chef who cooked our meal trained in Italy.)
Why? "Who cooked our meal" specifies which chef. No commas.
This park which is located in the city center is a great place for a picnic.
ND (This park, which is located in the city center, is a great place for a picnic.)
Why? "This park" is specific. Its location is extra information. Needs commas.
Coffee which is grown in many tropical countries is a popular beverage worldwide.
ND (Coffee, which is grown in many tropical countries, is a popular beverage worldwide.)
Why? We are talking about coffee in general. The clause adds an extra fact. Needs commas.
The company where my father works is expanding to Europe.
D (The company where my father works is expanding to Europe.)
Why? "Where my father works" defines which company. No commas.
The city where the conference will be held is preparing for many visitors.
D (The city where the conference will be held is preparing for many visitors.)
Why? "Where the conference will be held" defines which city. No commas.
My sister who works as a software engineer lives in Seattle.
ND (My sister, who works as a software engineer, lives in Seattle.)
Why? "My sister" is specific (implying I have one). Her job is extra information. Needs commas.
Students who finish their exam early can leave quietly.
D (Students who finish their exam early can leave quietly.)
Why? "Who finish their exam early" defines which students can leave. No commas.
The day when we met was unusually warm for October.
D (The day when we met was unusually warm for October.)
Why? "When we met" specifies which day. No commas.
The year when World War II ended was 1945.
D (The year when World War II ended was 1945.)
Why? "When World War II ended" specifies which year. No commas.
Spanish which is spoken by millions of people is a beautiful language.
ND (Spanish, which is spoken by millions of people, is a beautiful language.)
Why? "Spanish" is a specific, identified language. The number of speakers is an added detail. Needs commas.
People who are kind to others are often happier.
D (People who are kind to others are often happier.)
Why? "Who are kind to others" defines which people. No commas.
The car that is parked in the disabled bay doesn't have a permit.
D (The car that is parked in the disabled bay doesn't have a permit.)
Why? "That is parked in the disabled bay" specifies which car. No commas.
Mr. Peterson our math teacher is retiring this year.
ND (Mr. Peterson, our math teacher, is retiring this year.)
Why? "Mr. Peterson" is identified by name. "Our math teacher" is an appositive that gives extra information. Needs commas.
Dogs that are properly trained make excellent companions.
D (Dogs that are properly trained make excellent companions.)
Why? "That are properly trained" defines which dogs. No commas.
Friday which is my favorite day of the week is finally here.
ND (Friday, which is my favorite day of the week, is finally here.)
Why? "Friday" is specific. The opinion about it is non-essential. Needs commas.