Interjections are one of the traditional parts of speech (along with nouns, verbs, etc.), although some linguists have considered them not to be a part of language but rather instinctive reactions to a situation. The word interjection comes from the Latin interjicere “to throw between,” as they were seen as words that were tossed into a sentence, without being syntactically related to other items. Examples of English interjections are oh!, ah!, ugh!, and ouch! Interjections such as these, which are not (zero-)derived from words belonging to other parts of speech, and which have only an interjectional function, are called primary interjections; interjections that have evolved from words of other classes and which have retained their original function in addition to their new one are known as secondary interjections. Secondary interjections are often swear words, e.g. shit!, or religious terms, e.g. Jesus! Some (putative) interjections, interjectional phrases, consist of more than one word, e.g. my God!; they could be problematic for the view that interjections are a word class or part of speech. Interjections have received considerably less attention from linguists than the other parts of speech. This may be due, in part, to the just mentioned view that they are not really linguistic items and thus are of little or no interest from a linguistic point of view. However, to say that they have been neglected, as some authors do, is an overstatement; as can be seen in this article, scholars have been thinking and writing about different aspects of interjections for a long time (and note that this article mentions only works devoted (at least in large part) to interjections, not works on other subjects that also discuss interjections). Thus here one will see works on the phonetics/phonology, syntax, semantics, and pragmatics of interjections, among other subjects. There does, however, seem to be one gap in the literature: few, if any, papers focus on the morphology of interjections. A problem in compiling a bibliography on interjections is that authors disagree on what should be included in the set of interjections; for example, are onomatopoeias interjections (and thus should works on onomatopoeias be included in a bibliography on interjections)? In this article a conservative policy has been taken, and works dealing only with onomatopoeias (or greetings, etc.) have been excluded.