A concordance is an alphabetical list of the main words in a book or group of writings. It shows every place each word appears, along with the words around it. In the past, concordances were made only for important works, like the Vedas, Bible, Qur'an, or writings by Shakespeare, James Joyce, or ancient Greek and Latin authors. This was because creating a concordance before computers was very time-consuming, difficult, and expensive.

A concordance is more than an index. It includes extra information, such as explanations, definitions, and cross-references to related topics. This makes creating a concordance a long and detailed process, even with the help of computers.

Before computers, there were no search tools. A concordance helped readers find specific words in long texts, like the Bible, in a way similar to using a search engine today. Now, with technology that allows people to search for multiple words at once or find words near other words, interest in concordances has decreased. Also, methods like latent semantic indexing, which use math to analyze word meanings based on their context, have been suggested as alternatives.

A bilingual concordance is one made from texts that have been translated into two languages and aligned side by side.

A topical concordance lists subjects covered in a book, such as the Bible, along with the parts of the text where those subjects are discussed. Unlike a regular concordance, the exact word being searched does not need to appear in the text. The most famous example is Nave's Topical Bible.

The first concordance for the Bible was made for the Vulgate by Hugh of St Cher, who died in 1262. He had 500 friars help him. In 1448, Rabbi Mordecai Nathan finished a concordance for the Hebrew Bible, which took ten years. A concordance for the Greek New Testament was published in 1546 by Sixt Birck, and one for the Septuagint was created by Conrad Kircher in 1602. The first English Bible concordance was published in 1550 by John Merbecke. According to Cruden, this concordance did not use verse numbers created by Robert Stephens in 1545, but a concordance by Mr. Cotton did. Later, Cruden's Concordance and Strong's Concordance were published.

Use in linguistics

Concordances are often used in the study of language when analyzing texts. For example:

Concordancing methods are commonly used in large collections of texts from different countries, such as the American National Corpus (ANC), British National Corpus (BNC), and Corpus of Contemporary American English (COCA), which are available online. Programs that use concordancing methods are called concordancers or more advanced tools known as corpus managers. Some of these programs include tools that identify parts of speech (POS taggers) and allow users to create their own collections of texts with parts of speech labeled, which can be used for different types of searches in the study of language.

Inversion

The process of rebuilding some texts from the Dead Sea Scrolls used a concordance. Access to certain scrolls was controlled by a "secrecy rule," which limited viewing to the original International Team or their chosen representatives. After Roland de Vaux died in 1971, his successors refused to allow other scholars to publish photos of the scrolls. This restriction was overcome in 1991 by Martin Abegg, who used a computer to reverse a concordance of missing documents created in the 1950s. This concordance had been obtained by scholars outside the International Team, and it helped Abegg create a rough copy of the original text for 17 documents. Soon after, the original texts of the scrolls were released.