Indo-European language and Natural language

Indo-European language noun - The family of languages that by 1000 BC were spoken throughout Europe and in parts of southwestern and southern Asia.

Natural language and Indo-European language are semantically related. In some cases you can use "Natural language" instead a noun phrase "Indo-European language".

Natural language noun - A human written or spoken language used by a community; opposed to e.g. a computer language.

Indo-European language and natural language are semantically related. Sometimes you can replace phrase "Indo-European language" with "Natural language", this phrases are similar.