The term coordination refers to the juxtaposition of two or more conjuncts often linked by a conjunction such as and or or. The conjuncts (e.g., our friend and your teacher in Our friend and your teacher sent greetings) may be words or phrases of any type. They are a defining property of coordination, while the presence or absence of a conjunction depends on the specifics of the particular language. As a general phenomenon, coordination differs from subordination in that the conjuncts are typically symmetric in many ways: they often belong to like syntactic categories, and if nominal, each carries the same case. Additionally, if there is extraction, this must typically be out of all conjuncts in parallel, a phenomenon known as Across-the-Board extraction. Extraction of a single conjunct, or out of a single conjunct, is prohibited by the Coordinate Structure Constraint. Despite this overall symmetry, coordination does sometimes behave in an asymmetric fashion. Under certain circumstances, the conjuncts may be of unlike categories or extraction may occur out of one conjunct, but not another, thus yielding apparent violations of the Coordinate Structure Constraint. In addition, case and agreement show a wide range of complex and sometimes asymmetric behavior cross-linguistically. This tension between the symmetric and asymmetric properties of coordination is one of the reasons that coordination has remained an interesting analytical puzzle for many decades.
Within the general area of coordination, a number of specific sentence types have generated much interest. One is Gapping, in which two sentences are conjoined, but material (often the verb) is missing from the middle of the second conjunct, as in Mary ate beans and John _ potatoes. Another is Right Node Raising, in which shared material from the right edge of sentential conjuncts is placed in the right periphery of the entire sentence, as in The chefs prepared __ and the customers ate __ [a very elaborately constructed dessert]. Finally, some languages have a phenomenon known as comitative coordination, in which a verb has two arguments, one morphologically plural and the other comitative (e.g., with the preposition with), but the plural argument may be understood as singular. English does not have this phenomenon, but if it did, a sentence like We went to the movies with John could be understood as John and I went to the movies.
A Note on Wilder's (2008) Multiple Dominance Analysis of the Right Node Raising Construction