Idioma vs. lengua vs. lenguaje
Spanish, like many other languages, has multiple ways to express the concept of 'language'. These are through the words 'idioma', 'lengua', and 'lenguaje'. While they all refer to language in one form or another, there are certain nuances that distinguish them from each other.
Idioma
This term refers specifically to a complete system of verbal and written communication used by a particular region or country. It is often used interchangeably with 'lengua'.
El inglés es mi segundo idioma.
(English is my second language.)
Existen muchos idiomas en el mundo.
(There are many languages in the world.)
Lengua
This word is used to refer to a specific language, especially in linguistic or academic contexts. It can be used interchangeably with 'idioma'. Additionally, 'lengua' also means tongue in the physical sense.
Estoy estudiando la lengua española.
(I'm studying the Spanish language.)
Nuestra lengua materna es importante para nuestra identidad cultural.
(Our mother tongue is important for our cultural identity.)
Lenguaje
'Lenguaje' refers more broadly to the system of communication, verbal or non-verbal, used by a particular group or community. It includes body language, sign language, computer languages etc.
El lenguaje de señas es muy importante para la comunicación con las personas sordas.
(Sign language is very important for communication with deaf people.)
El lenguaje corporal también revela mucho sobre una persona.
(Body language also reveals a lot about a person.)
Summary
'Idioma' and 'lengua' are often used interchangeably to refer to a specific spoken or written language such as English or Spanish. The word 'lengua' can also refer to the physical organ that is used for speech and taste. On the other hand, 'lenguaje' refers more generally to systems of communication including but not limited too spoken and written languages.