Practical tip: that vs which

Michael Quinion on World Wide Words writes:

“Older grammar books make two firm points about the difference between the two types of clause:

  1. Restrictive clauses are introduced by that and are not separated from the rest of the sentence by commas.
  2. Non-restrictive clauses are introduced by which and must be separated by commas from the rest of the sentence to indicate parenthesis.

Which is correct?

“To our knowledge, it is the only body in the solar system which currently sustains life, although several other bodies are under investigation.”

“To our knowledge, it is the only body in the solar system that currently sustains life, although several other bodies are under investigation.”

Note the different nuances of meaning:

The painting that was hanging in the foyer was stolen. (It was the foyer painting that was stolen, not the kitchen or living room ones.) 

The painting, which was hanging in the foyer, was stolen. (The painting being the one we were discussing.)

The Van Gogh that was hanging in the foyer, which we purchased in 1929 for $10 000, was stolen.

 

References:

DailyWritingTips. [Internet accessed 30.05.2011, 3.8.2017]
Available from: https://www.dailywritingtips.com/that-vs-which/

Lawler J. That vs. which [Internet accessed 30.05.2011, 3.8.2017] English Grammar FAQ. University of Michigan.
Available from: http://www-personal.umich.edu/~jlawler/aue/xmasthat.html

Quinion M. Which Versus That: When to use each in subordinate clauses. [Internet accessed 30.05.2011, 3.8.2017 World Wide Words © 1996–2011.
Available from: http://www.worldwidewords.org/articles/which.htm

Sevastopoulos J. Clauses. [Internet accessed 30.05.2011, 3.8.2017] Grammar Quizes. Palo Alto, California USA.
Available from: http://www.grammar-quizzes.com/clauses-5.html

That Versus Which. [Internet accessed 30.05.2011, 3.8.2017] Illinois Institute of Technology. Chicago-Kent College of Law.
Available from: http://www.kentlaw.edu/academics/lrw/grinker/LwtaThat_Versus_Which.htm