Final answer:
The question is about the subject of Language. The phrase in line 3 refers to the nature of language and how it changes over time.
Step-by-step explanation:
The subject of the question is Language.
In line 3, the phrase "which alters when it alteration find" refers to the nature of language and how it changes over time. The word "alters" indicates that language is not static, but constantly evolving.
This demonstrates that language is not a fixed entity, but rather a dynamic system that adapts and changes as society and culture change.