A science? Or mathematics?

Chess is neither a science nor a mathematical exercise. Nor is it an art.

It is a craft, in which the practitioner's skill is as important as the material he works with.

Math is explicit, and chess is too hard for that, even when engines play.

Science likes to make practical assumptions for the sake of making a problem tractable, so between the two it's science.

One thing non-players don't understand is it's also a performance. Pros peak in their 30s. In other words the stronger player isn't only the one with more knowledge and experience, there's also a performance aspect at the board. Because of this people call chess partly a sport as well as an art and a science.

In any case, yes, it's fun how chess blends these things together. It has a little something for everyone.

Also during play it's fun how long term goals (strategy) blend seamlessly with short term considerations (tactics). You're also often exchanging one thing for another, like development for material, material for space, space for initiative/attack, attack for structure, and then you win the endgame due to structure. Trying to get the best value for your trade while blending short and long term considerations, plus the aesthetic beauty of e.g. geometrically based tactics is fun.

Your answer is too practicable for those who always want to make chess into something it is not, although have not a clue what subbuteo is and not sure I want to know. 

Clearly, Chess is neither maths nor science. This notion is nothing more than wishful thinking. You can take Anything and Everything and make claim it is somehow related to math as "all things have a mathematical explanation." Same can be said for science as science is nothing more than objective measurements of observation. 

Chess is chess and nothing more nor less. A board game. A hobby, something to idle our time with.

You can spend all day making analogies of what chess is like, trying to elevate it to a higher status as math or science. Chess can be favorably compared to a tree. This does not make chess a tree, or Anything else but a board game. Period. That computers are playing chess is basic. . Chess is a simple tool by which programmers can make verifiable, reliable tests because of the games complexity. 

You only Wish that chess had more meaning, possibly a purpose or that by playing chess implies a greater intelligence. It is a myth that chess promotes greater learning skills, increases comprehension and all the rest of it. There are no empirical studies to indicate as such. Only speculation and assumption. Learning to apply yourself in anything, will naturally have beneficial results. There exists nothing inherently "special" in chess. It is a board game. It is not math nor science. It is a natural tendency to place more importance on ones own choice of a hobby, job, or field of study, etc. This does not change what something is and what it is not. 

I have been playing chess, in all its forms for 50+ years because I Enjoy it. I understand what it is and what it is not. I don't try to make it into something above and beyond. Likewise, I've lost as many games as won and take it all in stride. For those who continue playing beyond a few years, rid themselves of preconceptions of what chess "is" and get past the "something to prove" phase,  find a lifelong Hobby to enjoy. 

Theoretically you could simplify chess to a boolean equation using sop (sum of products minimization) on a karnaugh map.  The sheet of paper big enough to hold that map though might occupy a measurable percentage of the solar system or maybe even a galaxy however, if you were using a standard font.

@blueemu - like your comment. It looks like perfect math formula - simply and elegant

Chess: A mystery that people and supercomputers are trying to solve.

Sure, chess can be expressed in mathematical terms. Might take a galaxy sized paper ! After all; it took 320 pages to prove 1 + 1 = 2. 

But the actual playing of the game is another matter entirely. We can express anything mathematically, But the terms used is not the game itself.

@Titled_Patzer - very well said, pure wisdom to learn from

Sure a joyless reductionist analysis would say it's nothing more and nothing less than a game... and so would a 5 year old. Adults can think beyond what's right in front of them and can see that, while still a game, we can talk about chess in terms of science, sport, etc.

Science is about gaining useful knowledge in a systematic way to solve problems. Chess can be like that.

 You use math to evaluate chess. Conclusion: chess is related to both math and science, but it's just a board game.. 

i think chess not relate with sc or math anymore

Cooking is science (chemistry} and the kitchen is s laboratory.. That's how some of the people commenting here think.