Czech (čeština, historically also Bohemian; lingua Bohemica in Latin), is a West Slavic language of the Czech–Slovak group, that is strongly influenced by Latin and German. It is spoken by over 10 million people and is the official language of the Czech Republic. Czech is closely related to Slovak, to the point of being mutually intelligible to a very high degree.

The Czech-Slovak group developed within West Slavic in the high medieval period, and the standardisation of Czech and Slovak within the Czech–Slovak dialect continuum emerges in the early modern period. In the later 18th to mid-19th century, the modern written standard was codified in the context of the Czech National Revival. The main vernacular, known as Common Czech, is based on the vernacular of Prague, but is now spoken throughout most of the Czech Republic. The Moravian dialects spoken in the eastern part of the country are mostly also counted as Czech, although some of their eastern variants are closer to Slovak.

The Czech phoneme inventory is moderate in size, comprising five vowels (each short or long) and twenty-five consonants (divided into "hard", "neutral" and "soft" categories). Words may contain uncommon (or complicated) consonant clusters, including one consonant represented by the grapheme ř, or lack vowels altogether. Czech orthography is simple, and has been used as a model by phonologists.

Thai, also known as Siamese or Central Thai, is the national and official language of Thailand and the native language of the Thai people and the vast majority of Thai Chinese. Thai is a member of the Tai group of the Tai–Kadai language family. Over half of the words in Thai are borrowed from Pali, Sanskrit and Old Khmer. It is a tonal and analytic language. Thai also has a complex orthography and relational markers. Spoken Thai is mutually intelligible with Laotian (Language of Laos; the two languages are written with slightly different scripts, but are linguistically similar).

Arabic (Arabic: العَرَبِيَّة‎‎, al-ʻarabiyyah or Arabic: عَرَبِيّ‎‎ ʻarabī) is a Central Semitic language that was first spoken in Iron Age northwestern Arabia and is now the lingua franca of the Arab world. Arabic also is a liturgical language of 1.7 billion Muslims. It is one of six official languages of the United Nations. It is named after the Arabs, a term initially used to describe peoples living from Mesopotamia in the east to the Anti-Lebanon mountains in the west, and from northwestern Arabia to the Sinai in the south.

Arabic is considered, in its standard form and dialects, a single language; it is spoken by perhaps as many as 422 million speakers (native and non-native) in the Arab world, making it one of the six most-spoken languages in the world.

The modern written language (Modern Standard Arabic) is derived from the language of the Quran (known as Classical Arabic or Quranic Arabic). It is widely taught in schools and universities, and is used to varying degrees in workplaces, government, and the media. The two formal varieties are grouped together as Literary Arabic, which is the official language of 26 states and the liturgical language of Islam. Modern Standard Arabic largely follows the grammatical standards of Quranic Arabic and uses much of the same vocabulary. However, it has discarded some grammatical constructions and vocabulary that no longer have any counterpart in the spoken varieties, and has adopted certain new constructions and vocabulary from the spoken varieties. Much of the new vocabulary is used to denote concepts that have arisen in the post-Quranic era, especially in modern times.

Arabic is written with the Arabic alphabet, which is an abjad script and is written from right-to-left although the spoken varieties are sometimes written in ASCII Latin from left-to-right with no standardized orthography.

Arabic has influenced many languages around the globe throughout its history. Some of the most influenced languages are Persian, Turkish, Urdu, Kurdish, Bosnian, Kazakh, Bengali, Hindi, Malay, Maldivian, Indonesian, Pashto, Punjabi, Tagalog, Sindhi and Hausa and some languages in parts of Africa. During the Middle Ages, Literary Arabic was a major vehicle of culture in Europe, especially in science, mathematics and philosophy. As a result, many European languages have also borrowed many words from it. Many words of Arabic origin are also found in ancient languages like Latin and Greek. Arabic influence, mainly in vocabulary, is seen in European languages, mainly Spanish owing to both the proximity of Christian European and Muslim Arab civilizations and 800 years of Arabic culture and language in the Iberian Peninsula, referred to in Arabic as al-Andalus. Balkan languages, including Greek, have also acquired a significant number of Arabic vocabulary through contact with Ottoman Turkish.

Arabic has also borrowed words from other languages including Greek and Persian in medieval times, contemporary European languages such as English and French in modern times.

Greek (Modern Greek: ελληνικά, elliniká, "Greek", ελληνική γλώσσα, ellinikí glóssa, "Greek language") is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems.

The Greek language holds an important place in the history of the Western world and Christianity; the canon of ancient Greek literature includes works of monumental importance and influence for the Western canon such as the epic poems Iliad and Odyssey. Greek is also the language in which many of the foundational texts in science, especially astronomy, mathematics and logic, and Western philosophy, such as the Platonic dialogues and the works of Aristotle, are composed; the New Testament of the Holy Bible was written in Koiné Greek. Together with the Latin texts and traditions of the Roman world, the study of the Greek texts and society of antiquity constitutes the discipline of Classics.

During antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and beyond. It would eventually become the official parlance of the Byzantine Empire and develop into Medieval Greek. In its modern form, the Greek language is the official language in two countries, Greece and Cyprus, a recognised minority language in seven other countries, and is one of the 24 official languages of the European Union. The language is spoken by at least 13 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora.

Greek roots are often used to coin new words for other languages; Greek and Latin are the predominant sources of international scientific vocabulary.

Polish (język polski, polszczyzna) is a West Slavic language spoken primarily in Poland and is the native language of the Poles. It belongs to the Lechitic subgroup of the West Slavic languages. Polish is the official language of Poland, but it is also used throughout the world by Polish minorities in other countries. It is one of the official languages of the European Union. Its written standard is the Polish alphabet, which has 9 additions to the letters of the basic Latin script (ą, ć, ę, ł, ń, ó, ś, ź, ż). Polish is closely related to Kashubian, Silesian, Upper Sorbian, Lower Sorbian, Czech and Slovak.

Although the Austrian, German and Russian administrations exerted much pressure on the Polish nation (during the 19th and early 20th centuries) following the Partitions of Poland, which resulted in attempts to suppress the Polish language, a rich literature has regardless developed over the centuries and the language currently has the largest number of speakers of the West Slavic group. It is also the second most widely spoken Slavic language, after Russian and just ahead of Ukrainian.

In history, Polish is known to be an important language, both diplomatically and academically in Central and Eastern Europe. Today, Polish is spoken by over 38.5 million people as their first language in Poland. It is also spoken as a second language in western parts of Belarus, Lithuania and Ukraine, as well as northern parts of the Czech Republic and Slovakia. Because of the emigration from Poland during different time periods, most notably after World War II, millions of Polish speakers can be found in countries such as Australia, Brazil, Canada, the United Kingdom, Ireland, and the United States. There are 55 million Polish language speakers around the world.