L1, or "Language 1," refers to a person's first language or mother tongue. It is the language that individuals learn from birth and typically use in their daily lives. L1 plays a crucial role in shaping a person's identity, culture, and communication skills. In the context of linguistics, L1 acquisition is the process through which children learn their first language naturally, often through interaction with family and caregivers. This process is fundamental to cognitive development and influences how individuals learn additional languages, known as L2 or "Language 2."