How are Turkish, Azerbaijani, Turkmen, and Gagauz related?

Turkish, Azerbaijani, Turkmen, and Gagauz are all members of the Oghuz branch, which constitutes the southwestern division of the Turkic language family.12

Within this branch, these languages are further categorized by their specific groupings:

• West Oghuz group: This group includes Turkish (spoken in Turkey, Cyprus, and the Balkans), Azerbaijani (spoken in Azerbaijan and Iran), and Gagauz (spoken in Moldova and Bulgaria).1
• East Oghuz group: This group includes Turkmen (spoken in Turkmenistan and adjacent countries).1

Historically, these languages share a common origin linked to the Oghuz confederation of Turkic peoples, who migrated from Central Asia and Mongolia toward Iran, Anatolia, and other regions starting around the 11th century. While they share close similarities in phonology, morphology, and syntax, they are distinct from other branches of the Turkic family, such as the northwestern (Kipchak), southeastern (Uyghur-Chagatai), and northeastern (Siberian) branches.3412