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When traveling it is a great experience to talk to locals and make friends. Sometimes also emergencies and unforeseen situations require one to ask for help and seek assistance.
In most cases of course, the official language of a country is the safest bet if one wants to be sure to be well-prepared for any situation and make the most of one's stay in a country.
On the other hand, it is unreasonable to assume tourists would learn the official language of each country they visit. Language acquisition takes a large amount of motivation, time and resources, which a holiday trip in general doesn't allow.
From a general point of view, what (approx.) 3 languages are the most useful to learn to communicate in the most places in the world?
Some of my thoughts on this:
- English is the most obvious choice, since it has the most L2 speakers and is spread over most of the world, i.e. it is not concentrated in one country.
- Mandarin or Cantonese might have the most L1 speakers, but the use is quite limited to China itself. Unless the trip goes to China, it might not make much sense to spend the time to learn those languages.
- German for example might be useful, since it is spoken in several countries. However, most German speakers (or Europeans, for that matter), have a good knowledge of foreign languages and are likely to know English or French. Therefore, German is probably also not necessary to learn.
- Russian is a language I could see make the list; it widely spoken in many countries, especially in places where English is not prominent and the official language has few speakers (Estonian, Bulgarian, Tajik, etc.)