Learn Spanish (Latin America): El chino es un idioma interesante.

In Spanish, when you talk about a language as the subject of a sentence or in a broad sense, you usually put the definite article (el) in front of it. So, "Chinese is..." translates to El chino es....

Why is it un idioma? Doesn't the -a at the end make it feminine?

Usually, yes! Words ending in -a are almost always feminine. However, idioma is one of a few rule-breakers (many of which come from ancient Greek) that end in -ma but are actually masculine. That's why it takes un instead of una. Another very common example you will see is el problema.

Why does interesante come after idioma?

In English, we put the descriptive word before the noun ("an interesting language"). In Spanish, descriptive adjectives almost always come after the noun they describe. So, you say un idioma interesante (literally "a language interesting").

Since idioma is masculine, shouldn't interesante change its ending?