Relative clauses of which the predicate contains a present, past, or passive participle can be used in a reduced form. Although it has been shown that participial relative clauses cannot always be considered to be non-complete variants of full relative clauses, they are generally called reduced relative clauses in the literature. Since they differ from full relative clauses in containing a non-finite predicate, they are also called non-finite relative clauses. Another type of non-finite relative clause is the infinitival relative clause. In English, in participial relative clauses, the antecedent noun is interpreted as the subject of the predicate of the relative clause. Because of this restriction, the status of relative clause has been put into doubt for participial adnominal modifiers, especially, because in a language such as English, they can occur in pre-nominal position, whereas a full relative clause cannot. While some linguists analyze both pre-nominal and post-nominal participles as verbal, others have argued that participles are essentially adjectival categories. In a third type of analysis, participles are divided into verbal and adjectival ones. This also holds for adnominal participles. Besides the relation to full relative clauses and the category of the participle, participial relative clauses raise a number of other interesting questions, which have been discussed in the literature. These questions concern the similarity or difference in interpretation of the pre-nominal and the post-nominal participial clause, restrictions on the type of verb used in past participial relative clauses, and similarities and differences between the syntax and semantics of participial clauses in English and other languages. Besides syntactic and semantic issues, participial relative clauses have raised other questions, such as their use in texts. Participial relative clauses have been studied from a diachronic and a stylistic point of view. It has been shown that the use of reduced forms such as participial relative clauses has increased over time and that, because of their condensed form, they are used more in academic styles than in colloquial speech. Nonetheless, they have proven to be used already by very young children, although in second language acquisition they are used late, because their condensed form is associated with an academic style of writing. Since passive or past participles often have the same form as the past tense, it has been shown that sentences containing a subject noun modified by a post-nominal past or passive participle are difficult to process, although certain factors may facilitate the processing of the sentence.