Online translators can be lifesavers when you need something incomprehensible translated into your native language, but they have severe limitations and therefore extremely limited applications.
There are numerous problems with online translators, but the most important is quite simply that they cannot understand context, so for any word that has more that one possible translation - which is the majority of words - the translator cannot know which meaning is required. Most machine translators just give the most common translation of each word, though they might provide the user with other possibilities so that it's up to the user to make the final call.
Google Translate goes a step further and uses sophisticated algorithms to determine the most likely translation of a given word in a given context. It's able to do this thanks to its staggering database of texts with official (human-created) translations (such as for the UN or European Union). Yet even that falls short, since these texts are mainly to do with topics like economics and politics. Things like casual conversations and slang are rarely available in official parallel versions, so even the mighty Google Translate often has to fall back on mathematical calculations of the most likely translation for any given word.
Pitfalls of automatic translators
Let's take a look at some real examples to give you a taste of the problem.
For example, let's say I want to translate "the paint is too light." Now, the adjective "light" at least three common French translations:
- clair (not dark)
- basses calories (not high-calorie)
- léger (not heavy)
But you know immediately that I mean the color of the paint is too light (not dark enough), right? Let's see what Google Translate says:
Oops, it says that the paint isn't heavy (plus it didn't make léger agree with the feminine noun). Not good. The correct translation is la peinture est trop claire.
Now consider "novel idea." If I look it up like that, with no article (which is how most people would probably look it up), Google says
Wrong! But look what happens if I add the article:
Even more intriguing, see how it changes in phrases:
In all of the above, we know that "novel" means "new, original" but Google doesn't, which makes it clear that the third example must have been manually programmed. Now multiply that effort by the literally infinite number of word combinations, and you can start to appreciate the sheer enormousness of this task.
And this is the best translator of the bunch! Here are the results for some others:
So even with these simple examples, there are already several errors in word choice, word order, and basic grammar (not to mention bizarreries like Babylon's "que's"). Now image translating a paragraph or page: the problems will increase exponentially.
Of course software can be programmed to recognize some contexts, but since there are infinite word combinations, it's simply impossible for there to be a complete database of translations. I have no doubt that someone at these companies will eventually spot and manually correct these errors, but there will always be thousands more waiting to take their places.
How to use online translators
Again, this isn't to say that online translators are useless - far from it. As long as you're aware of the pitfalls, there are a few ways you can use them.
1. When you receive a message in a foreign language, you can get a good sense of the meaning by running it through a translator. It probably won't be idiomatic, but since it's now in your native language, you can usually read between the lines to get the gist of it.
2. If you have some idea of how to say something in a foreign language, try pasting your attempt into a translator to see how it's "reverse translated," which might give you some idea about major mistakes you've made. One really great site that you can check with is Linguee - paste your translated text and see how similar phrases have been rendered in official translations. But again, if you're writing anything of importance, be sure to check with a native speaker!
3. You can get translations of simple words and check spelling/accents with a translator, but since the latter only involves one language, a dual-language tool is likely to be overkill. You're probably better off with an online dictionary, which will provide multiple options with context and examples.
The bottom line
You can use online translators to get the gist of a message for your own purposes or to check on something short and simple, because you're aware of the limitations. But you should never auto translate and send a message into a language you don't speak, because you really have no idea what that translation says or how it will be received. Instead, you should either hire a translator or send it in the original language. Let the recipient auto translate it, if they need to - at least that way, you're not responsible for whatever nonsense (or worse!) ends up on their screen.