Celtic languages refer to a branch of Indo-European languages that are spoken in different parts of Europe. While there are several languages under this category, some possible synonyms for the term 'Celtic language' include Gaelic tongues, Celtic tongues, and Celtic tongues of the British Isles. Further alternatives may include modern or ancient variations, such as Welsh, Breton, Irish, Scottish, and Manx Gaelic. Notably, while some of these languages are still widely spoken, others have reached critical levels of endangerment. With Celtic languages being so diverse, alternative versions of the term may be useful in communicating specific linguistic focus.