The history of the Bulgarian language is divided into three periods: old, middle, and modern. The Old Bulgarian Period lasted from the 9th century through the 11th century, and the texts from this period make up the bulk of the Old Church Slavic texts, their colloquial, popular variant. The Middle Bulgarian Period lasted from the 12th century through the 14th century. The Modern Bulgarian Period started in the 15th century, but the modern literary language, which is quite different from Old Bulgarian, formed only during the 19th century. Modern Bulgarian's two major dialect groups are the eastern and western dialects, each subdivided into north and south varieties. The modern literary language is based primarily on the northeastern dialects.

Bulgarian has several traits that make it unique (together with Macedonian) among the Slavic languages. Due to severe Greek language influence it has a definite article that comes after the noun (as do the Scandinavian Germanic languages) - for example, in Bulgarian: zhena (woman) and zhenata (that woman, the woman). Bulgarian lost the case system that existed in Common Slavic, the language from which all Slavic languages descended. In Bulgarian languages, as in English, prepositions have replaced cases as a way of showing the grammatical relationships between different parts of a sentence-for example, in Bulgarian: knigata za zhenata (the book about the woman) and dadoh knigata na zhenata (I gave the book to the woman). All that happened because of longtime Greek influence. But the language, however, have preserved the Common Slavic vocative form.

Bulgarian verbs have a large variety of tenses, including present, future, future perfect, future in the past, perfect, pluperfect, imperfect, and aorist, in addition to an imperative, a verbal adverb, and various participles. The infinitive form of the verb has been lost. The language has a special set of verb forms that indicate that an event has not been witnessed or is not vouched for - for example: Ivan napravi tova (Ivan did that, and I witnessed it or vouch for the truth of the statement) and Ivan napravil tova (Ivan is alleged to have done that, but I did not witness the act or do not want to vouch for the truthfulness of the statement).