Non-restrictive Clauses with Which

First reconstruct the simple statement: we refer to the appendix → the appendix to which we refer. Formality changes the preposition’s position, not the verb’s complement pattern. Depend on or depend upon gives on which or upon which; refer to gives to which.

Abstract nouns also have established patterns: to a certain extent → the extent to which; under these conditions → the conditions under which. Prepositions are not arbitrary decorations. In spatial contexts, in, at and under can create different true descriptions: choose the one that accurately identifies the position.

When a relative clause refers to a thing, a fronted preposition takes which rather than relative that. Do not leave only the preposition without a relative pronoun. Subject and predicate normally follow which; the order does not become interrogative.

This restriction concerns relative that. Ordinary After that, we left is correct: that means the preceding situation and does not introduce a relative clause. For a person, the typical formal pattern is preposition + whom; which is not universal after all prepositions.

Preposition + which can occur in a defining relative clause identifying a thing or a clause adding extra information. If the description answers “which one among several?”, use no commas.

If the thing is already uniquely identified, set off the extra information with commas. Inside a sentence, two commas are needed. Do not automatically add them merely because which appears or the style is formal: that can change how the reader identifies the thing.

When formalising, move the existing preposition before which and remove its old copy. Do not repeat it or them after the verb for the same thing, already represented by which. Other objects needed by the meaning can remain.

Preserve negation, time frame, participants and strength of claim. Changing which to that and adding strictly are different edits: strictly adds intensity rather than repairing a relative construction. When joining sentences, retain both sets of facts without accidentally strengthening either.

Not every which needs a preposition. In the report which I read, read takes a direct object, so invent no preposition. Nor can every where mechanically become in which: distinguish departure from a place, movement to it and presence in it.

Do not move a phrasal-verb particle as though it were a preposition. In give up a habit, up belongs to the verb meaning “abandon”: the habit which I gave up. Up which I gave does not express this pattern. Complex phrasal-prepositional verbs are not developed into a separate topic here.

Name the thing which refers to. Reconstruct a simple statement and check the preposition: depend on the grant, refer to the table, work under the conditions. If that relationship does not work, correct the meaning before the word order.

Then check the text’s purpose: is formal fronting needed, and does the description identify the thing or merely add information? Your own message can use different natural words and structures while preserving meaning and the preposition’s relationship to the verb or noun.

When which is the comment’s subject, the verb follows: which helped, which was helpful. When which is the object, the clause needs its own subject: which we welcomed, which nobody had predicted. The formula which + verb describes only the first pattern.

Do not duplicate the same role with it: in which we welcomed, which already represents what we welcomed. The separate subject we is necessary. Agreement also depends on the role: which was refers to one situation; in which the organisers were expecting, were agrees with organisers.

In an ordinary connected written sentence, separate this comment with a comma before which. Do not replace which with that or what, or omit it, even when it is the object.

In conversation, Which was nice can stand as an added comment on a preceding turn. Such an utterance is not universally ungrammatical. However, tasks asking for one complete written sentence require it to be attached with a comma. Punctuation marks the boundary; you must still check what the pronoun refers to.

Check what the comment describes, not just the punctuation. In The scanner, which is portable, fits in a bag, which describes scanner. There is a comma, but this lesson targets reference to the whole fact rather than a noun’s property.

Sometimes two readings are possible: a company announced profits that increased share prices, or the announcement itself caused the increase. A comma alone does not always remove this ambiguity. To comment clearly on the event, provide an intelligible context and rephrase the statement if necessary.

Combining sentences does not license changing facts. If the original says may, do not automatically present the consequence as already realised. If it says did not, the comment concerns the absence of the action.

Which does not itself mean because. The comment’s predicate creates the relationship: caused expresses causation, was disappointing an assessment, we had expected an earlier expectation. Do not turn an assessment into a consequence or add a new date.

Take two statements: We started late. This reduced our discussion time. Replace only the referring word This with which and join the second clause with a comma. Check that the first fact is unchanged and that it is what explains the comment.

Another natural option is We started late, and this reduced our discussion time. This is grammatical. If a task explicitly requires a comment with which, it misses that learning target but is not a grammatical error. Similarly, the delay can express a related meaning, but a following which may then refer to the noun rather than the whole statement.

First identify the fact your listener needs to understand, then add only the necessary comment: a consequence for a plan, your reaction or what was expected. A brief which was helpful works when it is clear what helped. Avoid chaining several which clauses with unclear references.

Check your own text: can you identify the whole fact before which? Does the comment logically concern that fact? Is there an unnecessary it? Are time, negation and possibility preserved? Is there a comma in the written sentence? Models in open exercises guide self-checking; they are not the only acceptable answers.

In an ordinary defining relative clause about things, with no preposition directly before the relative word, both that and which are possible. Changing one to the other does not itself turn a defining clause into a non-defining one. Which alone does not automatically require commas.

Some house styles require that in defining clauses and reserve which for non-defining clauses. Follow such a requirement when explicitly specified for a text. It is a style convention, not a general ban on defining which, and not a universal rule of American English.

In modern neutral written English, a non-defining clause about things uses which, not that. This is where the choice between the two words is grammatically restricted.

If a non-defining clause appears within a sentence, use two commas: one before which and one after the whole relative clause. The second returns the reader to the main clause. Do not separate the relative word from its predicate with a comma.

If the additional information ends the sentence, use one comma before it and the usual full stop at the end. Do not add a second comma before the full stop. These exercises practise comma punctuation specifically, although other editing contexts sometimes allow brackets or dashes for parenthetical information.

Do not set off a defining relative clause with commas. This does not mean the entire sentence must contain no commas: a comma may belong to an introductory phrase or another construction.

A non-defining clause signals that the reader can identify the referent without that clause. The item may have been mentioned, pointed to, or made clear by the situation. My car, which… does not prove that the owner has only one car.

With a plural noun, an entire set may already be identified by an earlier statement. The additional property applies to that set, not to every such item in the world.

A defining clause selects the group about which a statement is made, but usually does not say what happened to the rest. The files which were corrupted were restored asserts that the corrupted files were restored. It does not assert that no uncorrupted files were restored, and it gives no file count.

In a defining clause, the relative word can be omitted when it is the object: the report (that / which) I read. The subject I is already present, and the omitted word corresponds to the object of reading. The zero-pronoun version needs no commas.

If that or which is the relative clause's subject, simple omission is not possible: the report that arrived, not the report arrived in this relative construction. This does not ban the separate sentence The report arrived; it is a requirement for the relative-clause link.

Do not omit the pronoun in a non-defining clause, even when it is the object. Do not duplicate it with a separate it or they in the same grammatical role: which I read already contains the object, while which arrived contains the subject.

When a preposition directly precedes the relative word referring to a thing, use which: on which, with which. On that does not fit this relative construction. This is a restriction on the preposition's position, not evidence that every which-clause is supplementary. Full stylistic restructuring with prepositions is practised separately.

Which can also comment on the entire preceding fact: in The screen froze, which delayed the presentation, the freezing caused the delay, not the screen itself. This is also a supplementary relative comment with a comma, but its reference is an event rather than a noun. Non-defining and referring to the whole fact are not mutually exclusive categories.

If which could theoretically refer to either an item or an event, do not guess the intended meaning. Add context or rephrase. The main skill here is making the reference and message boundaries clear, not assigning an arbitrary single label to an ambiguous sentence.

Before correcting a sentence, identify the meaning to preserve. In The boxes, that arrived today, are upstairs, you can replace that with which to retain an additional statement about already identified boxes. Or you can remove both commas, selecting the boxes by their arrival time. Both results are grammatical, but they are not the same editorial change.

In a work email or instruction, first identify the item clearly enough. Then decide whether the following property selects it or merely adds information. For a defining clause, choose an appropriate that, which, or omitted object pronoun. For a non-defining clause, use which and mark the full boundaries of the addition.

When checking your work, read only the main clause, then restore the relative clause. Has the intended set of items changed? Have you added an inference about the number or the fate of the remaining items? Model open answers show one possible solution; other natural wording and structures are acceptable when they meet the stated goal.