If your main purpose of learning foreign languages is the ability to speak to as many people as possible in their native language, then knowing the top ten languages spoken throughout the world is important.
From Wikipedia:
| Rank | Language | Family | Ethnologue (2005 estimate) | Encarta estimate |
|---|---|---|---|---|
| Tenth | German | Indo-European, Germanic, West | 95.4 million | 100.1 million |
| Ninth | Japanese | Japanese-Ryukyuan | 122 million | 125 million |
| Eighth | Russian | Indo-European, Slavic, East | 145 million | 167 million |
| Seventh | Portuguese | Indo-European, Italic, Romance | 177.5 million | 176 million |
| Sixth | Hindi | Indo-European, Indo-Iranian, Indo-Aryan | 181 million | 366 million |
| Fifth | Arabic | Afro-Asiatic, Semitic | 206 million | 422 million |
| Fourth | Bengali | Indo-European, Indo-Iranian, Indo-Aryan | 230 million | 207 million |
| Third | English | Indo-European, Germanic, West | 309 million | 341 million |
| Second | Spanish | Indo-European, Italic, Romance | 322 million | 322 million |
| First | Mandarin | Sino-Tibetan, Chinese | 873 million | – |
I’m sure you see the disputes in the number of speakers for each language between Ethnologue and Encarta. There are a number of factors that come into play when building a list such as this, none of which I will discuss here — they are far too boring.
There are certainly other lists available for different purposes. If you want the most useful languages to learn RIGHT NOW, this is certainly not the list. You may have entirely different reasons for learning another language, or multiples. Whatever your reason, that’s the most important one. Now, get to learning your next language!
Please see the Wikipedia source for more and the most up-to-date information on the matter.