In non-functional linguistics, a sentence is a textual unit consisting of one or more words that are grammatically linked. In functional linguistics, a sentence is 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 opposes that of the curve, which is delimited by phonologic features such as pitch and loudness and markers such as pauses. This notion also opposes a clause, which is a sequence of words that represents some process going on throughout time. This entry is mainly about sentence in its non-functional sense, though much work in functional linguistics is indirectly cited or considered such as the categories of Speech Act Theory. A sentence can include words grouped meaningfully to express a statement, question, exclamation, request, command or suggestion.A sentence is a set of words that in principle tells a complete thought (although it may make little sense taken in isolation out of context); thus it may be a simple phrase, but it conveys enough meaning to imply a clause, even if it is not explicit. For example, "Two" as a sentence (in answer to the question "How many were there?") implies the clause "There were two". Typically a sentence contains a subject and predicate. A sentence can also be defined purely in orthographic terms, as a group of words starting with a capital letter and ending in a full stop. In the teaching of writing skills (composition skills), students are generally required to express (rather than imply) the elements of a sentence, leading to the schoolbook definition of a sentence as one that must [explicitly] include a subject and a verb. For example, in second-language acquisition, teachers often reject one-word answers that only imply a clause, commanding the student to "give me a complete sentence", by which they mean an explicit one. As with all language expressions, sentences might contain function and content words and contain properties such as characteristic intonation and timing patterns. Sentences are generally characterized in most languages by the inclusion of a finite verb, e.g. "The quick brown fox jumps over the lazy dog".