In Star Trek, what system automatically converts speech between different languages?

In Star Trek, the universal translator automatically converts speech between different languages.

The device allows humans, Vulcans, Klingons, Ferengi, and many other species to communicate despite having unrelated languages. It is commonly portrayed as a handheld or built-in computer system that analyzes speech patterns and produces an understandable translation almost immediately.

Star Trek rarely treats translation as perfect. Some languages are difficult to process, and unusual biology, metaphor, cultural references, or deliberate deception can confuse the system. The technology also helps explain why crews can communicate with civilizations they have never previously encountered.

The universal translator is separate from subspace communication. Subspace radio carries a message over interstellar distances, while the translator interprets the language at the receiving end. Different Star Trek series present the device with varying levels of visibility, but its basic function remains consistent throughout the franchise.