Una lengua viva : sistema uniforme y rígido, ya que por lo general presenta variaciones según el lugar geográfico (dialectos), el medio social (sociolectos), y los individuos (idiolectos), y por cierto, también variaciones en el tiempo (diacronía), lo que hace que, considerado un momento dado, una lengua está siempre en evolución.

dialecto - habla - lengua - lenguaje

Great answer Sr ! I'm also passionate about languages, I really love them, especially those ones from Europe. ​

Thank you, Johana. It's something slightly different I'm trying to say. It's not the use of the word language in other contexts like music and signal language. I'm preparing a short video to introduce myself as an Italki Community Tutor, and I'd like to say that I love everything about language and languages. You can say that in English using the same word, but I don't think it would make any sense in Spanish to say 'Me encanta todo sobre la lengua y las lenguas'. What about 'Me encanta todo sobre los idiomas y el estudio de lenguaje.' ?

You can use both "lengua" or "lenguaje". You say "lengua" or "idioma" when referring to a spoken language like English language, French language, German language, etc. You say "lenguaje" when referring to a capacity to communicate something like musical language, spoken language, signal language, etc.