Update 1: FAQs were added at the bottom of this page. PDF version of all these FAQs can be downloaded from this post.
S Translator simply translate what your type or speak to another language. S4 can speak in the translated language.
Currently, 9 languages are fully supported, i.e,. both text-to-speech, and speech-to-text. These 9 languages are Chinese, French, German, Italian, Japanese, Korean, Portuguese, Spanish, and English. It seems works quite well on S4.
However, compared with Google Translate, I found S Translator has no improvement for the supported languages. I do not understand why Samsung tries to reinvent the wheel. Google Translate supports more than 60 languages. It also supports text-to-speech in conversation mode.
Most importantly, you can download offline languages and use Google Translate when you have no data connections. However, S Translate need data connection to function.
FAQs on S Translator
Q1 : Can I use the S translator when the device isn’t connected a data network?
A : No, You need to turn on the data network connection or use a wireless LAN connection (Wi-Fi) because S translator operation is supported by an internet-server.
(FYI: Google Translate can work offline).