Koine is the Greek word for "common." Koine Greek (also called New Testament Greek) was the form of the Greek language used from around 300 BC to AD 300. The books of the New Testament were originally written in Koine Greek. Koine Greek was the lingua franca (or the commonly used language of communication) in the Mediterranean and Middle Eastern for hundreds of years following the conquests of Alexander the Great, including during the time of the early church.
Claims have been made that the Greek language of the New Testament confused many scholars for a period of time but this is not the case. It was, however, sufficiently different from Classical Greek that some hypothesized that it was a combination of Greek, Hebrew, and Aramaic. An attempt was made to explain it as a "spiritual language," assuming that perhaps God created a special language just for the Bible. But studies of Greek papyri found in Egypt over the past 120 years have shown that the Greek of the New Testament manuscripts was the "common" (koine) language of the everyday people - the same as that used in the writing of wills and private letters. In fact, Koine Greek was propagated through the centuries by the Eastern Orthodox Church and was the language common in the Byzantine Empire. Therefore, knowledge of the language was never lost nor was the meaning of any of the vocabulary in doubt when reformation scholars began to translate from the Textus Receptus.
Koine Greek spread throughout the Mediterranean and Middle East as a result of the conquests of the Greek armies of Alexander the Great. It served as a second language for many people and had become the language of communication throughout much of the Roman Empire and beyond by the time of Jesus. It retained its role as the lingua franca until the Middle Ages.
The Old Testament was translated into Koine Greek between the third and first centuries before Christ. This translation is known as the Septuagint, or simply, the "LXX". The New Testament books were originally written in Koine Greek. Below is part of a passage from the New Testament - John 1:1
Diphthongs and ι-subscripts
There are also version of several vowels with a small iota underneath (or beside in the case of capitols): ᾼ ᾳ, ῌ ῃ, ῼ ῳ. It is believed that these represent ancient diphthongs, but the pronunciation is not altered in the time of any Greek writing we can know.
Accents and Breathing
There are three possible accents that can be put on Greek vowels: the acute ´, the grave (pronounces 'grahv') ` and the circumflex. The circumflex should like an upside crescent over the vowel, but some fonts use the caron (^) or even the tilde (~). It is thought the these different symbols represented rising and falling pitch, like modern Chinese, but by the time of our literature, they only indicate accent or stress.
Over the initial syllable of word that begins with a vowel, there will always be either a rough (‘) or a smooth (’) breathing sign. Rough means a 'h' sound and smooth means a lack of extra sound. A 'Ρ' (Rho), in the initial position, also taking a breathing sign, typically the rough. How precisely this altered pronunciation is not known.
There a many resources available for the study of the Bible in Koine Greek.
There are numerous ancient manuscripts containing parts or all of the New Testament. Not all of these manuscripts are identical for a variety of reasons. For example, sometimes a scribe copying an older manuscript would make a spelling or grammatical error. The German Bible Society produces a work that contains what a number of well known scholars believe is the most likely representation of the original New Testament, known as the NA27 or the UBS4 version.
The language itself is studied widely throughout theological colleges. Well known textbooks include the series by William Mounce.
Numerous internet resources also exist. One of the most used resources is the ReGreek project by Zack Hubert. This site was closed down in March 2009 due to copyright issues.