Reference desk

The words behind the answers.

Short, plain-English definitions for the terms used in our tools and explainers. No jargon loop where one unknown word leads to another.

PDF

PDF/A: An ISO standard for long-term archiving. A PDF/A file embeds fonts and avoids features that depend on external software, so it should look the same years from now. It is not the right format for everyday editing.
Redaction: Permanently removing visible content from a document. Drawing a black box over text does not redact it; the text may still be selectable underneath. True redaction removes the underlying data before sharing.
OCR: Optical character recognition. It turns an image of text, such as a scan, into selectable text. OCR does not change how a page looks, but it makes searching and copying possible.
Flattening: Merging interactive layers such as form fields, annotations and signatures into the page itself. A flattened PDF is harder to edit but displays more consistently across devices.
Page range: A way to describe which pages to keep, such as 1-3, 5, 8-10. Ranges are usually read from the start of the document, so page 1 is the first page even if it has no printed number.
Linearized PDF: A PDF arranged so the first page can display before the whole file downloads, also called Fast Web View. It matters for large files viewed over a slow connection, not for local editing.

Amortization: Paying off a loan in scheduled installments. Early payments are mostly interest; later payments are mostly principal. A shorter term or extra payments shift that balance faster.
PMI: Private mortgage insurance. US lenders often require it when a down payment is below 20 percent. It protects the lender, not the borrower, and usually ends once the loan balance is low enough.
Escrow: An account that holds money for a specific purpose, such as property taxes and homeowners insurance. A mortgage servicer may collect a monthly escrow amount and pay the bills when they come due.
APR: Annual percentage rate. It expresses the cost of borrowing as a yearly rate, including some fees. APR is useful for comparing offers, but it is not the same as the interest rate or the monthly payment.

BMI: Body mass index, a ratio of weight to height. It is a quick screening measure for adults, not a diagnosis. It does not account for muscle, pregnancy, children or body composition differences.

Large language model: A machine-learning model trained on large amounts of text to predict and generate language. It learns statistical patterns rather than storing a lookup table of facts, which is why it can sound confident and still be wrong.
Token: A chunk of text, often a word or part of a word, that a language model processes. Models have token limits, and usage is often measured in tokens rather than characters or words.
Encryption: Scrambling data so only someone with the right key can read it. Encryption protects data in transit and at rest, but it does not stop a trusted app from reading what you enter while it is open.

Percentage: A fraction expressed out of 100. Twenty percent means 20 out of every 100, or 0.20. Percentages are useful for comparisons, but the base matters: 10 percent of a small number can be less than 5 percent of a large one.
Percentage point: The difference between two percentages, measured directly. Going from 10 percent to 12 percent is a rise of 2 percentage points, but a 20 percent relative increase. Mixing the two exaggerates or hides changes.
US customary units: The measurement system common in the United States: inches, feet, yards, miles, ounces, pounds, gallons and Fahrenheit. Some names match imperial units but the volumes differ, especially for gallons.
Tipping: An optional payment above the bill, common in US restaurants and some services. Custom varies, and a tip is not the same as a service charge, which is usually added automatically.

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