From an historical perspective, the Spanish lexicon consists of three different categories: (1) its historical core of words inherited from the Latin spoken in the Roman province of Hispania; (2) loanwords that entered Spanish over its long history as a result of contact at the levels of both oral and written discourse with other languages; and (3) words created internally through such mechanisms of derivational morphology as suffixation, prefixation, compounding, back-formations, and so on. Over the last 150 years, specialists in the history of the Spanish language have studied in considerable detail all three sources of lexical material. Although most of the lexical items inherited from spoken Latin have cognates in many (in some cases, all) of the Romance languages, Spanish has preserved some words that live on only in Spanish (and neighboring Portuguese) or only in Spanish, Portuguese, and Romanian, the geographical extremes of the Romance-speaking world, far removed from the centers of linguistic innovation. As a result of language contact, loanwords from the pre-Roman languages of the Iberian Peninsula, Visigothic, Arabic, Gallo-Romance (northern and southern French), Portuguese, Catalan, Italian, classical Latin, native languages of the New World, and English have entered and taken root in the Spanish lexicon. Although such lexical borrowings have often been studied within a cultural framework, recent research has focused on their introduction and incorporation as examples of contact-induced language change at the level of the lexicon. Throughout its history, Spanish has increased the size of its vocabulary through the creation of neologisms through processes of suffixation, prefixation, and composition. The study of such items has traditionally been the focus of specialists in diachronic derivational morphology. This subfield constitutes in many respects an important component of diachronic lexicology. Indeed, etymology and diachronic derivational morphology are two sides of the same coin. Lexical history is not limited to the study of additions to the vocabulary. Over time, many words have fallen into disuse or have become obsolete. Some recent work on the history of the Spanish lexicon has examined the various external and internal/structural causes of lexical loss in the history of the Spanish lexicon.