The chapter discusses the application of complex systems theory to natural language, emphasizing its ability to encode and transmit information about hierarchical structures in the universe. It highlights that natural language, particularly in written form, embodies the essence of complexity, making it a central subject in quantitative studies within the science of complexity. The review covers three main research trends in quantitative linguistics: 1. **Word Frequencies and Scaling**: The impact of punctuation on scaling violations in Zipf’s law is addressed, with Mandelbrot’s correction being used to restore scaling. 2. **Time Series Analysis**: Methods inspired by time series analysis are used to study long-range correlations in written texts, revealing features often found in complex systems, such as fractal and multifractal structures. 3. **Network Formalism**: The application of network theory to natural language is reviewed, focusing on word-adjacency networks that reflect word co-occurrence in texts. These networks can be used for classification and semantic analysis, showing significant differences from random networks. The chapter also discusses the impact of punctuation on the statistical properties of language and its information-carrying ability, suggesting that punctuation should be considered on par with words. The review concludes by emphasizing the interdisciplinary nature of language studies, highlighting the contributions of mathematics, physics, and other fields in understanding and quantifying the complexity of natural language.The chapter discusses the application of complex systems theory to natural language, emphasizing its ability to encode and transmit information about hierarchical structures in the universe. It highlights that natural language, particularly in written form, embodies the essence of complexity, making it a central subject in quantitative studies within the science of complexity. The review covers three main research trends in quantitative linguistics: 1. **Word Frequencies and Scaling**: The impact of punctuation on scaling violations in Zipf’s law is addressed, with Mandelbrot’s correction being used to restore scaling. 2. **Time Series Analysis**: Methods inspired by time series analysis are used to study long-range correlations in written texts, revealing features often found in complex systems, such as fractal and multifractal structures. 3. **Network Formalism**: The application of network theory to natural language is reviewed, focusing on word-adjacency networks that reflect word co-occurrence in texts. These networks can be used for classification and semantic analysis, showing significant differences from random networks. The chapter also discusses the impact of punctuation on the statistical properties of language and its information-carrying ability, suggesting that punctuation should be considered on par with words. The review concludes by emphasizing the interdisciplinary nature of language studies, highlighting the contributions of mathematics, physics, and other fields in understanding and quantifying the complexity of natural language.