"Who" = for people (the one who, who); "that" = for things or animals (that, which).
Relative pronoun: used to introduce a relative clause describing a PERSON. "The man who called" = the man that called (but "who" is preferred for people). "The student who won the prize" = the student that won (formal writing prefers "who" for people). In formal English, WHO is always used for people.
The engineer who designed the bridge received a national award for innovation.
She is the kind of person who always finds the positive side of any situation.
Anyone who wishes to participate should sign up before the end of the week.
Relative pronoun: used to introduce a relative clause describing a THING, ANIMAL, or IDEA (not a person). "The book that I read" = the book I read. "The dog that barked" = the dog that barked. In informal English, "that" is sometimes used for people, but formal writing prefers "who" for people.
The proposal that was submitted last week has already been approved by the committee.
They adopted the dog that had been living at the shelter for the longest time.
The idea that money cannot buy happiness is more complicated than it first appears.
Common mistake
Very common error: "The person that called" instead of "The person who called". In informal and colloquial English, "that" for people is widely accepted. However, in formal writing — academic, professional, journalistic — using "who" for people and "that" for things is the established norm. "The employee that was promoted" (informal, accepted). "The employee who was promoted" (formal, preferred). Never use "which" for people: "the employee which was promoted" is always incorrect.
Trick to remember it
The rule is simple: PERSON = WHO. THING = THAT. Test: "Can I shake hands with it?" If yes = person = WHO. If no = thing = THAT. The book cannot shake hands, it is a THING: "the book THAT I read." The engineer can shake hands, she is a PERSON: "the engineer WHO designed it." For animals: in formal English, named animals or pets with personality can use "who"; generic animals typically use "that".
Quick rule
Who = for people (and sometimes named animals with personality). That = for things, concepts, and generic animals. Never "which" for people.
Did you know?
The who/that distinction for people vs things has become more fluid in modern English. Several corpus linguistics studies show "that" for people appearing in written English since the 14th century. Canonical authors including Shakespeare, Chaucer, and the King James Bible use "that" for people regularly. The modern preference for "who" for people was codified mainly by 19th and 20th century prescriptive grammarians. Today, the most important style guides (AP, Chicago, APA) prefer "who" for people in formal writing.
Exercise 1 · Pick the right one
The consultant _____ advised us to restructure the department later admitted the plan had never been tested.
Exercise 2 · Pick the right one
The software _____ the team developed over two years was sold for far less than its actual market value.
Exercise 3 · Form the word
Who = for people (and sometimes named animals with personality). That = for things, concepts, and generic animals. Never "which" for people.
Very common error: "The person that called" instead of "The person who called". In informal and colloquial English, "that" for people is widely accepted. However, in formal writing — academic, professional, journalistic — using "who" for people and "that" for things is the established norm. "The employee that was promoted" (informal, accepted). "The employee who was promoted" (formal, preferred). Never use "which" for people: "the employee which was promoted" is always incorrect.
The rule is simple: PERSON = WHO. THING = THAT. Test: "Can I shake hands with it?" If yes = person = WHO. If no = thing = THAT. The book cannot shake hands, it is a THING: "the book THAT I read." The engineer can shake hands, she is a PERSON: "the engineer WHO designed it." For animals: in formal English, named animals or pets with personality can use "who"; generic animals typically use "that".
Bryan López
Founder of SpeakUP Academy