F# (Pronounced as F Sharp)

Microsoft pronounces F# as its succinct, type-inferred, expressive, efficient functional and object-oriented language for the .NET platform. F# is developed as a research programming language to provide the much sought-after combination of type safety, succinctness, performance, expressivity and scripting, with all the advantages of running on a high-quality, well-supported modern runtime system. This combination has been so successful that the language is now being transitioned towards a fully supported language on the .NET platform. Some of the reasons for this move are that F# gives you:
*  Succinct, type-inferred functional programming, 
*  Interactive scripting like Python and other languages, 
*  Foundations for an interactive data visualization environment, 
*  Combination of type inference and safety, like that of ML, 
*  A cross-compiling core shared with the popular Objective Caml language, 
*  A performance profile like that of C#, 
*  Easy access to the entire range of powerful .NET libraries and database tools, 
*  A foundational simplicity with similar roots to Scheme, 
*  Option of a top-rate Visual Studio integration, which is usable with the freely available Visual Studio 2008 Shell 
*  Experience of a first-class team of language researchers with a track record of delivering high-quality implementations, 
*  Speed of native code execution on the concurrent, portable, and distributed .NET Framework.

F# was developed as a pragmatically-oriented variant of ML that shares a core language with Objective Caml. Unlike other scripting languages it executes at or near the speed of C# and C++, making use of the performance that comes through strong typing. Unlike many type-inferred, statically-typed languages it also supports many dynamic language techniques, such as property discovery and reflection where needed. F# includes extensions for working across languages and for object-oriented programming and it works seamlessly with other .NET programming languages and tools.

Ref: http://research.microsoft.com/en-us/um/people/curtisvv/fsharp_default.aspx