Which: adding a description of a thing

Why use which?

When two statements concern the same thing, you can combine them without repeating the noun. In The camera which is on the shelf is mine, which is on the shelf describes camera and helps identify the intended camera.

Which is not asking a question here. It is a relative pronoun, connecting a noun to a clause that describes it. The descriptive clause normally follows its noun directly.

How to build it

name of a thing, animal or idea + which + description

The camera which is on the shelf is mine.

Which is on the shelf identifies which camera is meant.

I found the file which you need.

Which you need adds information about file without repeating the file.

The advice which helped me was simple.

Advice does not refer to a person, so which is a suitable explicit relative pronoun.

A thing, animal or idea, rather than a person

Which usually refers to an inanimate object, an animal or an abstract thing: a phone, a dog, a plan, some advice. Who is the typical choice for a person. First identify the noun before the relative clause, then choose the pronoun.

In a defining description that identifies the thing being discussed, that can often replace which: The phone that I bought works well. Both versions are correct.

How to build it

person → who; thing, animal or idea → which; that is also possible in a defining clause

clause: A construction with a verb, often with its own subject: when I arrived. A non-finite clause may leave the subject unspoken: to get home.

The dog which sleeps by the door is very calm.

Which can describe an animal. In ordinary speech, who also occurs for pets when they are treated as individuals.

The plan which saves the most time is option B.

Plan refers to an idea rather than a person, and which introduces its description.

The mechanic who repaired the bike called me.

Mechanic refers to a person, so use who here rather than which.

Which as the subject of the relative clause

In The app which sends reminders is free, which is the subject performing sends. The relative clause's verb follows it directly. Do not add another subject, it: which already represents the app within this clause.

Do not omit which when it is the subject. The app sends reminders is free lacks a grammatical connection between app and its description. A useful clue is that which is usually the subject when a verb follows it directly.

How to build it

name of a thing + which + verb

verb / V: A word for an action or state, such as work or be. The pattern determines its form.

The machine which makes coffee is broken.

Which is the subject of makes, so it is unnecessary before makes.

The button which deletes the file is red.

Which is the subject performing deletes and cannot be omitted.

The bus which stops here goes to the centre.

Which stops here identifies the intended bus.

Which as the object of the relative clause

In The film which we watched was funny, we is the relative clause's subject and which is the object of watched: we watched the film. A separate subject, we, therefore follows which.

In a defining clause, this object which can often be omitted: The film we watched was funny. Both versions are grammatical. If which remains, do not repeat the object with it: use which we watched, not which we watched it.

How to build it

name of a thing + which + separate subject + verb

subject / S: The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
verb / V: A word for an action or state, such as work or be. The pattern determines its form.

The jacket which I ordered arrived today.

I is the subject and ordered is the verb. Which represents the jacket as the object.

The report which Maya sent contains the figures.

The underlying idea is Maya sent the report, so do not add a repeated it in the relative clause.

The report Maya sent contains the figures.

Object which has been omitted from a defining clause without changing the meaning.

Identification or extra information?

A defining relative clause identifies exactly which thing is meant. In Use the printer which has a green label, the description selects one printer from several, so there are no separating commas. In such a clause, that may replace which, and object which can sometimes be omitted.

A non-defining relative clause adds information about a thing already clearly identified. In OfficePro, which is free, can open the file, the name OfficePro already identifies the application. Enclose the extra information in commas; do not omit which or replace it with that. These commas convey meaning rather than serving as optional decoration.

How to build it

identifying description: noun + which…; extra detail: known thing, which…, continuation

noun: A word naming a person, thing or idea: student, book, happiness.

Choose the chair which has wooden legs.

The description distinguishes this chair from the others, so there are no separating commas.

My bike, which is red, is easy to find.

My bike already identifies a particular bicycle in this context. Its colour is extra information enclosed in two commas.

The blue folder, which is on my desk, contains the receipts.

The speaker has already identified the blue folder. Which is on my desk adds a separate detail.

Using which in your own sentences

First name the thing. Then check that the relative clause is close to the intended noun, does not repeat it with it, and has a complete structure. If which performs the action, a verb follows it. If another person performs the action, a separate subject follows which.

Next decide the purpose: does the description select one thing from several or merely add detail about something known? That determines the commas. In an everyday defining clause, that or omitted object which may sound natural, but a response without which does not fulfil an exercise explicitly requiring which.

Which can also refer to an entire preceding clause: The train was late, which was annoying. This is a genuine use, but it is outside this rule's narrow A2 focus and is not assessed here.

How to build it

name the thing → add a which-clause → identify who acts → check meaning and commas

clause: A construction with a verb, often with its own subject: when I arrived. A non-finite clause may leave the subject unspoken: to get home.

Please send the photo which shows the label.

Which is the subject of shows, and the description selects the intended photograph.

Please send the photo which you took outside.

You is the subject of took; which is its object.

NoteBox, which works offline, is useful on trains.

The name already identifies the application, so two commas enclose the extra description.

Common mistakes

Incorrect:The phone who is on the desk is mine.

Correct:The phone which is on the desk is mine.

Phone refers to a thing, so the standard relative clause requires which rather than who.

Incorrect:The app which it sends reminders is free.

Correct:The app which sends reminders is free.

Which is already the subject of sends. Adding it creates two subjects for the same verb.

Incorrect:The folder which I opened it was empty.

Correct:The folder which I opened was empty.

Which already represents folder as the object of opened, so do not repeat it.

Incorrect:My bike, which is new needs repair.

Correct:My bike, which is new, needs repair.

Close the additional non-defining clause with a second comma before needs.

Sources