How many computer languages are currently in use and which among them is most widely used?

I am not sure of the complete total of computer languages in use in 2018 because i some countries outmoded languages will still be in circulation. However, to be effective in 2018 you need to consider learning the following languages. Java is probably no.1 90% or more of Fortune 500 virtually depend upon it. It's just found everywhere and its slogan is 'Write once, run anywhere" which obviously gives tremendous confidence.

Javascript is very widely used. It's been dominant in the field for some time and so many applications have been designed using it. There's also Python, a general purpose language that you'll find in machine learning, desk=top apps and so on. C++ is much older, but still popular because it's efficient, flexible and reliable. Ruby is a very well loved language producing clean and succinct code. Going to newer languages there's Rust, sponsored by Mozilla and Swift which is for developing iOs and MacOs systems.