SECAI Core · phase 4 of 15 · noun

Personally identifiable information

Data that can be used to identify or contact an individual (or, in the case of identity theft, to impersonate them).

The Explain card

Plain English: PII is any data that can single out, contact, or impersonate a specific person: names, addresses, ID numbers, biometrics, even birthday plus postcode.
Example: A customer support chatbot is fine-tuned on real ticket histories. Later, a tester asks for "an example of a refund request" and it replies with a real customer's name, phone number and address, lifted from the training data.
Why it matters: PII that leaks through a model output or a prompt log is a breach, with all the regulatory and reputational cost that implies. Defenders must track where PII enters training sets, prompts, embeddings and logs.
Hook: If it can point to a person, it is PII, and it has a way of resurfacing in model output.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

The redaction pipeline strips personally identifiable information from each support transcript before the fine-tune job starts.

Why these words

personally Latin personalis, of a person, from persona, a mask or character turns the stack toward a human being rather than a machine, a file, or a place
identifiable English from identify plus -able, identify from Late Latin identitas, sameness the -able adjective, so the head noun is qualified as able to be picked out as the same one
information Latin informatio, a giving of form, from informare, to shape or instruct the head noun, so the other two words qualify a payload rather than a person

Where it came from

Origin: US privacy-law collocation from Latin personalis (of a person, from persona, a mask), Late Latin identitas (sameness, from idem, the same) via identify plus -able, and Latin informatio (a giving of form)
Entered the language: 1970s
What changed: Personally had meant in one's own person since the late 1300s. Identifiable, built from identify plus -able, arrived around 1804 as able to be picked out as the same one. Information had meant instruction, then news, then the stuff a machine keeps. US privacy statutes of the 1970s stacked the three as a legal heading, and the phrase later sat beside Europe's personal data as the American label, often shortened to PII on forms and in incident reports.

How it is spelled

Pattern: y of -ify becomes i before -able: identify, identifiable
Pattern: -ally is -al plus -ly, adverb from adjective
Pattern: -tion from Latin -tio, with t as /ʃ/ in information
Pattern: personal keeps one n
Breaks the pattern: the noun phrase stays three words; hyphens appear only when the stack modifies another noun
Breaks the pattern: personally is an adverb modifying an adjective, a pairing English usually reserves for legal and medical writing
Breaks the pattern: personal keeps one n, while personnel, from the same persona, keeps two
Breaks the pattern: information is a mass noun here, so no plural even when the records are many

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

Privacy-law labels

Identifiable family

Information compounds

Phase 4: Data Integrity, Governance, and Provenance

Once you know what data is, learn the principles that keep it trustworthy, traceable, and minimized throughout its lifecycle.