ESEN
Which one to use?Advancedpronombre relativopronombre relativo
WhichvsThat
"That" introduces essential information; "which" introduces additional, non-essential information (set off by commas).
Side-by-side comparison
Which
pronombre relativo"That" is used in defining relative clauses (no commas): the information is necessary to identify the noun.
My car, which I bought last year, needs new tires already.
The Eiffel Tower, which was built in 1889, attracts millions of tourists every year.
The report, which took three weeks to complete, was well received by the board.
That
pronombre relativo"Which" is used in non-defining relative clauses (with commas): the information is additional about something already identified. In American English, "that" can also be used in defining clauses.
The car that you recommended turned out to be perfect for my needs.
I need a phone that has a long battery life.
The movie that won the Oscar last year is now available on streaming.
Common mistake
The rule in formal American English is clear: essential clause (no commas) = "that"; additional clause (with commas) = "which." In British English and informal speech the distinction is much more relaxed and both are used interchangeably.
Trick to remember it
Comma test: can you put commas around the clause and still have a complete main sentence? Yes = "which"; no (the clause identifies which specific thing we mean and cannot be removed) = "that."
Quick rule
- •That = essential clause, no commas (defines which one we mean).
- •Which = additional clause, with commas (extra information that can be removed).
Did you know?
This distinction was primarily codified by Henry W. Fowler in his influential "A Dictionary of Modern English Usage" (1926), where he argued that THAT should be used in restrictive clauses and WHICH in non-restrictive ones. Before Fowler, Shakespeare, Milton, and the King James Bible used THAT and WHICH interchangeably. Modern British English remains much more flexible than American English on this distinction, and many British style guides do not make the rule so rigid. The Fowlerian distinction is largely a 20th-century American academic English convention.
Practise what you learned
Exercise 1 · Pick the right one
The book _____ I borrowed from you was fantastic. Can I borrow another?
Exercise 2 · Pick the right one
The new restaurant, _____ opened last month, already has a waiting list.
Exercise 3 · Form the word
Related word pairs
WhovsWhom
"Who" is the subject (does the action); "whom" is the object (receives the action).
Who'svsWhose
'Who\'s' contracts 'who is' or 'who has'; 'whose' asks or states who something belongs to.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
A lot ofvsMany
'A lot of' works for countable and uncountable; 'many' only for countable; 'much' only for uncountable.
Bryan López
Founder of SpeakUP Academy