Relative clauses in the English language are formed principally by means of relative pronouns. The basic relative pronouns are who, which, and that; who also has the derived forms whom and whose. Various grammatical rules and style guides determine which relative pronouns may be suitable in various situations, especially for formal settings. In some cases the relative pronoun may be omitted and merely implied ("This is the man [that] I saw", or "This is the putter he wins with"). English also uses free relative clauses, which have no antecedent and can be formed with the pronouns such as what ("I like what you've done"), and who and whoever. Modern guides to English say that the relative pronoun should take the case (subject or object) which is appropriate to the relative clause, not the function performed by that clause within an external clause. Overview The basic grammatical rules for the formation of relative clauses in English are given here. More details can be found in the sections below, and in the article on who. The basic relative pronouns are considered to be who, which and that; but see an alternative analysis of that below. The relative pronoun comes at the very start of the relative clause unless it is preceded by a fronted preposition: "The bed on which I was lying". (It is normal to slide the preposition to the end of the clause and leave it stranded, or dangling: "The bed which I was lying on"). The relative clause may start with a larger phrase containing the relative pronoun after a preposition: "The bed, the owner of which we had seen previously, ...", or "The bed, lying on which was a small cat, ..." who is used only with its antecedent referring to a person ("The man who ..."); which, referring to a thing ("The flowers which ..."); that, referring to either a person or thing ("The woman that ...", or "The flowers that ..."). that is used only in restrictive relative clauses, and is not preceded by a comma ("The teacher that looks worn-out", or "The car that looks worn-out"); but who and which may be used in both restrictive and non-restrictive clauses, and may or may not take a comma ("The teacher who looks worn-out", or "My teacher, who ..."), and ("The car which looks worn-out", or "My car, which ..."). In some styles of formal English, particularly