Mathematica is a symbolic computation program used in many different scientific sectors. Thanks to Mathematica, we are able to perform complex mathematical calculations in a simple way.

What I like most is its console mode as it allows me to define my problems quickly.

Easy to learn but capable of very sophisticated operations and functionality. You can control threading, for example. The native functions are indicated by their capitalization. Symbols can be used (like Greek letters) as variables. Formatting options make complex expressions easier to follow. Interactive graphics -- you can give a seminar using a Mathematica notebook to illustrate your discussion. Image processing power added in the last ~5 years is impressive. Great support community, including example notebooks showing physical, biological, engineering, etc. processes and ideas.