(in parenthesis is what dndbeyond calls them):
Cozian (Common): Since ages ago, Cozian was treated as the international language, most places at adopting it in some form. This was established way back when Sarvelan Empire, Spire and Cozia were one united kingdom, which was a long time ago. Nowadays, there is a general 'northern' and 'southern' dialects spanning the northern or southern hemispheres of the world, as well as many regional accents. This is the sole official language for Kingdom of Cozia, Sarvelan Empire and City-State of Spire, and is co-official in most other countries.
Mesan (Khur): Mesan is an old language with many hissing sounds and hard clicks. As the name implies, it is the official language of Principality of Mesa, as well as the Grand Duchy of Shobern. In Mesa, however, it is co-official with Cozian.
Dalaian (Hadozee): Dalaian is a language adopted for underwater communication as much as over-water communication, its various tones and clicky sounds allowing it to be distinguishable even through the murkiness of water. Alongside Cozian, it is an official language in the Brotherhood of Dalai .
Tihubontan (Nerakese): Nerakese is a tonal language, considered to have the most bizarre sayings and the greatest variety of ways to swear without blasphemising. Alongside Cozian, it is the official language of the Theocracy of Tihubontu.
Bidisian Dialects (Naush): Sort of like chinese in real life, the Bidisian Dialects can be quite varied from region to region throughout the Bidisian Conglomerate, some being unrecognisable by others. Nonetheless, They all share many of the same roots and base words, especially words related to sailing, trading and the weather. Some of these words are so common that they slip into the Cozian language, the other official language in this country.
Celestial: Celestial is the Common equivalent for communication by and to the pantheon. Although worship varies from culture to culture and god to god, many places consider celestial to be the language of the gods, and should be used in prayers and worship. Most religious people (which is most people) know Celestial to some extent.
(lots of these are variations of Celestial, depending on different dieties)
Primordial: The language of the elements, can be split into the dialects of Aquan, Auran, Ignan, and Terran. They are usually used in worship of a respective elemental deity (Maer, Deity of Change, Ignis, Goddess of Civilisation, Terra, Goddess of the Wilderness, Auro, God of the Weave)
Sylvan: The language of the Fae and emotions. Usually used for worship specifically to Zheyli, God of Emotions. Fey-aligned creatures usually speak this, as well as the fey realm.