There are several classifications of Language. They are not mutually exclusive.
(1) Natural Language
(2) Foreign Language
(3) Universal Language (e.g. Esperanto)
(4) Spoken Language (e.g. Myanmar Sagar)
(5) Written Language (e.g. Myanmar Sar)
(6) Programming Language
(7) Scientific & Technical Language
(8) Business Language
(9) Specialty Language (e.g. for a domain)
(10) Meta Language (to describe a language)
(11) Body Language [comment provided by Dr. Kyaw Tint]
Chinese, English, Arabic … are some languages that are read and spoken by many people in the world.
There are often dialects of a language.
English is not our native language.
We had to take TOEFL (Test of English as a Foreign Language) to prove that we had a reasonably good command of English. It covered (a) Reading Comprehension (b) Listening Comprehension (c) Essay
Several Community Centers in the USA offer ESL (English as a Second Language).
Saya Des taught English at RIT. He did further studies in the UK. He taught “English as a Specialty Language” (aka ESL in Canada.)