In linguistics and grammar, a sentence is a linguistic expression, such as the English example "The quick brown fox jumps over the lazy dog." In traditional grammar it is typically defined as a string of words that expresses a complete thought, or as a unit consisting of a subject and predicate. In non-functional linguistics it is typically defined as a maximal unit of syntactic structure such as a constituent. In functional linguistics, it is defined as a unit of written texts delimited by graphological features such as upper-case letters and markers such as periods, question marks, and exclamation marks. This notion contrasts with a curve, which is delimited by phonologic features such as pitch and loudness and markers such as pauses; and with a clause, which is a sequence of words that represents some process going on throughout time. A sentence can include words grouped meaningfully to express a statement, question, exclamation, request, command, or suggestion. Typical associates Clauses A sentence is typically associated with a clause, and a clause can be either a clause simplex or a clause complex. A clause is a clause simplex if it represents a single process going on through time, and it is a clause complex if it represents a logical relation between two or more processes and is thus composed of two or more clause simplexes. A clause (simplex) typically contains a predication structure with a subject noun phrase and a finite verb. Although the subject is usually a noun phrase, other kinds of phrases (such as gerund phrases) work as well, and some languages allow subjects to be omitted. In the examples below, the subject of the outmost clause simplex is in italics and the subject of boiling is in square brackets. Notice that there is clause embedding in the second and third examples. [Water] boils at 100 degrees Celsius. It is quite interesting that [water] boils at 100 degrees Celsius. The fact that [water] boils at 100 degrees Celsius is quite interesting. There are two types of clauses: independent and non-independent/interdependent. An independent clause realises a speech act such as a statement, a question, a command or an offer. A non-independent clause does not realise any act. A non-independent clause (simplex or complex) is usually logically related to other non-independent clauses. Together they usually constitute a single independent clause (complex). For that reason, non-independent clauses are also called interdependent. For instance,