Kotlin is a programming language that can run on Java Virtual Machine. By using the LLVM compiler infrastructure it can be successfully compiled to Javascript source code. It was developed in 2011 in Saint Petersburg in Russia by a team of programmers from JetBrains who incidentally also developed the JetBrain IDE that Android is based on. Although it is not compatible with Java, it is interoperable with Java code and relies on it thus becoming a popular choice among developers. The best feature of Kotlin is that it works steadily with Java and C++ on Android. So using your existing code you can use the Android libraries adding Kotlin code to any of your projects.
Kotlin is perfect for developing Android applications providing the merits of a new and modern language for Android platform without any limitations:

Kotlin’s full compatibility with DK6 ensures a successful running of its applications with any Android device without any problems. Kotlin is fully compatible with the Android build system and totally supported on Android Studio.

Kotlin is similar to Java where similar bytecode structure is concerned so the speed of its application is equally fast. At times for inline functions, Kotlin’s code using lambdas is faster than the same code in Java.

Kotlin being totally interoperable with Java allows the use of already existent Android libraries in Kotlin applications like data binding, annotation process, and Dagger work.

Kotlin has a concise runtime and with the use of ProGuard it can be reduced further. The Kotlin runtime adds less than 100k to the size of an apk file in a real application.

Compiling Time
Effective incremental builds or compiling time in Kotlin are either equally fast if not faster than with Java.

Learning Factor
It is comparatively very easy for a Java developer to start with Kotlin. Converting from Java to Kotlin is an automatic process that is included in Kotlin plugin. A guide of the main features of the language with all interactive activities is found in Kotlin Koans.
An announcement has been made by Google that it is officially supporting Kotlin on Android as a top class language. Unlike other programming languages Google does not own Kotlin, but JetBrains will partner with Google to shield the language by setting up a nonprofit foundation. Besides Android Kotlin will target other platforms too like the native code on Macs and iOS and JavaScript for web development.
To conclude we can say that Kotlin is a great language along with being an excellent fit for Android, not only by giving the developers a free hand but also due to it matching the spirit of Android. Kotlin like Android is an open source project mainly under Apache 2 not belonging to any one company but involving the whole community at large.
Don’t over think, in case you are not using Kotlin just get started with Kotlin on Android. In fact Kotlin being adopted on Android has been continuously rising over the years among developers.
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