Usually, relative clause cannot stand alone as a sentence. In contrast to dependent clause, independent or main clause is a clause that can stand alone. Main clause is synonymous to a simple sentence. In essence, clause is the basic unit of meaning in the English language (Stuart-Smith, 2003). Either dependent or independent, a clause conveys a message. This paper, on the other hand, examines the relative clause as a basic unit of a language in relation to functional grammar, especially in the ideational metafunction level. Here, the use of the word clause will refer to dependent clause.
The usage of a clause in the different world languages differs greatly. There are three identified dimensions of these differences: (1) position of the clause with respect to the head noun or the noun being modified; (2) how a clause is marked; (3) the absence or presence of a pronominal reflex (Celce-Murcia & Larsen-Freeman, 1999, p.573). In the English language, a clause follows the head noun. For instance, in the sentence, "San Antonio is a city that has experienced very rapid growth," the head-noun San Antonio precedes the italicized clause. To place the clause before the head noun in a sentence sounds, if not ungrammatical, awkward. Farsi and Arabic languages share similar syntactic pattern in the clause usage compared to most European languages. However, Japanese and Korean languages do not adhere to the first dimension of the above-mentioned clause usage (Celce-Murcia & Larsen-Freeman, 1999, p.573).
In the second dimension, the English language employs a relative pronoun (e.g., who) or demonstrative pronoun (e.g., that) to mark that what follows is a clause (Celce-Murcia & Larsen-Freeman, 1999, p.573). For example, "I read the journal that you recommended." Or, "I love the girl who appreciates poetry." The lines before the demonstrative and relative pronouns are independent clauses that can stand as a sentence. The application of the pronouns that and who merely modify the head nouns. Besides English, Persian and Chinese languages use other forms of markers placed between the head noun and the clause. The presence or absence of the pronominal reflex is the third dimension along which languages differ in the clause usage (Celce-Murcia & Larsen-Freeman, 1999, p.573). In the sentence, "Art called out to the girl that he knew," the "that" replaces "the girl" in the embedded sentence, "he knew the girl."
Ideational metafunction is one of the three fundamental functional components of a language. Ideational metafunction is primarily concerned with the function that "language has of being about something" (Halliday & Hasan, 1976). In the past,
a theory of the fundamental functions of language have been developed, in which lexicogrammar can be subdivided into 3 broad metafunctions, namely: interpersonal, ideational and textual. Each of these 3 deals with a different aspect of the world, and they are concerned with various modes of clause meanings. "The ideational metafunction is about the natural world in the broadest sense, including our own consciousness, and is concerned with clauses as representations. The interpersonal metafunction is about the social world, especially the relationship between speaker and hearer, and is concerned