Relative pronouns are words like that and which, and they are used to replace a word or phrase in a previous phrase or sentence. Using relative pronouns correctly increases clarity, and makes a text more formal. It is important to note that that the use of these words in writing may differ slightly from their use in spoken English.
Do not put a comma before that.
Relative pronouns can function as objects in both restrictive and non-restrictive clauses. If the pronoun refers to a human, then the word "whom" is used. When the pronoun refers to a non-human thing, in which, where, and when are used.
The book in which these concepts are first described was published in 2010.
The relative pronoun where is used when a physical location is being referred to. Where is also sometimes used instead of in which when referring to a printed source. This usage is not incorrect, although it is less formal.
Runic artefacts can appear in a wide variety of materials, in contrast to rune stones where letters are carved onto naturally resistant material.
The book where these concepts are first described was published in 2010.
The relative pronoun when can be used if a time period is being referred to, although in which can also be used.
Interpretations of cultures are inevitably influenced by the historical period when they were made.
The phrase that which (or those which, in plural) and the word what can be used as pronouns to introduce a relative clause. The two alternatives are nearly equivalent in meaning, although that which is more formal than what.
Our conclusion is very much in line with that which others have made.
Our results are very much in line with those which have been found previously.
Our results are very much in line with what others have found.
In some cases, that which is clearly preferable to what.
When he first meets Daisy, his image of her and that of her house are closely connected because to him they both represent that which is forbidden.
Whenever the thing referred to is a human, it is more formal to use the relative pronoun who.
Expatriates who are new to a country will have much to learn.
Using that, while not incorrect, is somewhat less formal.
Expatriates that are new to a country will have much to learn.
In certain circumstance, who can be used instead of that, if the stylistic purpose is to anthropomorphize the referrent.
Firms who manage to attract high-level workers are undervalued be the market.
Things owned by a human or animal can be indicated by the word whose ("My sister, whose car I am borrowing, comes home tomorrow.") However, English has no word for things owned by an inanimate object. In these cases, the word whose can be used, although this usage is considered by some to be less formal. The alternative is to use the phrase of which. Using of which will require re-writing certain parts of the sentence, and even then, such a re-write is not always feasible.
The second chapter describes numerical prediction models used in Sweden today, whose accuracies contribute to the dependability of forecast products.
The second chapter describes numerical prediction models used in Sweden today, the accuracies of which contribute to the dependability of forecast products.
When using a relative pronoun to introduce a cause of something, one can use either why or that.
[T]here must be an underlying ideological, ritual, sociological, or political, if not operative, reason why the dead and/or those who have buried them would choose to mark a person in death in a particular way (Costin 1996:119).
How can I use corpora to improve my academic writing in English?
Scientific Writing: Why and How?