Stylometry
The statistical analysis of writing style to identify or distinguish authors, using measurable features such as sentence length, punctuation habits and how often particular function words appear.
Why it matters
Stylometry is the established discipline that AI detection borrows from, and knowing the difference explains why detection is weaker than it sounds: stylometry works on substantial bodies of text with a known set of candidate authors, and AI detection has neither.
A concrete example
Scholars have used stylometry for decades to argue about disputed authorship — comparing a contested text against large samples from a handful of candidates, looking at habits writers cannot consciously control. Applying the same idea to a 500-word essay with an open set of possible authors is the hardest version of the problem, not the easiest.
How to use it
Stylometry is the older discipline behind AI detection: identifying authorship from measurable style features such as sentence length, function-word frequency and punctuation habits. It has a long history in literary and forensic work, where it is applied to substantial bodies of text by a known set of candidate authors. That context matters, because it is exactly what AI detection lacks — a short passage and an open set of possible authors is the hardest case for these methods, not the easiest.
The common mistake
Assuming techniques that work on a novelist's collected works transfer to a 500-word essay. Stylometric confidence depends heavily on sample length and on having candidate authors to compare against; strip both away and the method is being asked to do something it was never reliable at.
Related terms
AI Detector
A tool that estimates whether a passage of text was generated by an AI model, by measuring statistical properties of the writing rather than by checking any record of its origin.
Perplexity
A measure of how surprising a piece of text is to a language model — roughly, how unexpected each word is given the ones before it. Low perplexity means the text follows predictable paths.
Burstiness
The variation in complexity and length across the sentences of a passage. Human writing tends to be bursty — long sentences next to short ones — while generated text tends to be more uniform.
Agentic AI
AI systems that operate autonomously over extended tasks — planning, executing, and self-correcting without step-by-step human guidance. Unlike chatbots, agentic AI sets sub-goals, uses tools, and adapts its strategy based on intermediate results.
AI Agent
An autonomous AI system that can perceive its environment, make decisions, and take actions to achieve goals — like managing your email, scheduling meetings, or monitoring data.
AI Disclosure
Stating that AI was used in producing a piece of work, where a policy, client or publisher requires it. Distinct from permission: some contexts allow AI use but require it to be declared.