There are several translation apps that are in common use between English and Vietnamese. Many of the Vietnamese use dictionary apps or apps that help with pronunciation. What I find most useful is the Google Translate App.
Tips to Make it Faster
There are a couple of tips to make this work faster. You can download the languages you use frequently to your phone. Then the app doesn’t always need to be online or using your data to make the translation. The camera now works directly in Vietnamese to English. Just open the app, click the camera, take an image and swipe across the text you want translated.
Vietnamese is Easy
Even though the app is free to use, I prefer the mobile website. Vietnamese is much easier to translate than the other languages in South East Asia because, thanks to the French, it is based on Latin characters. Thai, Laotian, Cambodian, Chinese and Japanese all use other alphabets.
The main problem with Vietnamese is pronunciation. Vietnamese uses diacritical (accent) characters, making a mistake on these can make a BIG difference in the translation. Fortunately, the app corrects most of these mistakes from the context. When you enter the letters, the app will usually suggest the correct phrase.
There is a keyboard for Vietnamese (Ti?ng Vi?t).
You can also use the two-language microphone to translate conversations in real-time. With a good WiFi connection, this can be really convenient.