Glossary : The words, explained.

A summary written in new words, the way a person would write one, rather than assembled from sentences copied out of the source. Modern AI summarizers mostly produce abstractive summaries.

Studying by pulling information out of memory, for example by answering a question, instead of reading it again. A 2013 review by Dunlosky and colleagues rated practice testing as one of only two high-utility learning techniques.

A shorter version of a video, article or document, written by an AI model. It keeps the main points and leaves out detail. An AI summary is a fast way to understand a source and should be checked against the original when a detail matters.

Captions created by speech recognition instead of being written by a person. YouTube generates them for many videos in the languages it supports. Their accuracy depends on audio quality, accents and whether people talk over each other.

Text shown in time with what is said in a video. Captions can be supplied by the creator or generated automatically. Tools that summarize YouTube videos, SumAI included, generally work from a video's captions.

The sections a video is divided into, each with a start time and a title. In SumAI, Chapters is also the name of a summary style that summarizes a long video section by section.

Asking questions about a document in a chat window and getting answers drawn from the text of that document, instead of searching or reading it page by page.

A diagram of ideas joined by labelled links that say how the ideas relate. It is a close relative of the mind map, and most research on learning with diagrams of this kind has studied concept maps.

A summary made by selecting the most important sentences from the source and presenting them unchanged. It stays close to the original wording, but it often reads less smoothly than an abstractive summary.

A way of studying named after the physicist Richard Feynman: explain a concept in plain language, as though teaching it to someone new, and notice where the explanation breaks down. Those gaps are what to study next.

A card with a question or prompt on one side and the answer on the other, used for testing yourself. Flashcards work best when you try to recall the answer before turning the card over.

A curve describing how memory of newly learned material falls away over time when it is not reviewed, steeply at first and then more slowly. It comes from Hermann Ebbinghaus's experiments in the 1880s, in which he memorized lists of nonsense syllables and measured how much time relearning them saved.

In AI, a statement produced by a model that is not supported by its source or by fact. In a summary, a hallucination is something the summary says that the original did not.

The points in a video where an important idea or a new topic begins, each marked with a timestamp and a short title. In SumAI, tapping a key moment jumps to that part of the video.

The kind of AI model behind modern chatbots and summarizers. It is trained on a very large amount of text and produces language by predicting what should come next.

A plain-text format that uses simple marks for structure, such as # for a heading and - for a list item. Because it is plain text, it moves easily between note-taking apps. SumAI can export summaries as Markdown.

A diagram with one central topic and branches for its subtopics and their details. It shows the structure of a subject at a glance. SumAI generates a mind map from each summary.

Software that recognizes the letters in an image or a scanned page and turns them into real, selectable text. A scanned PDF needs OCR before a text-based tool can read it.

Text in a PDF that is stored as characters, so that it can be selected, searched and read by software. A page that was scanned or photographed and saved only as an image has no text layer. SumAI needs PDFs with selectable text.

The panel that appears when you tap Share on an iPhone or iPad, listing the apps and actions you can send something to. SumAI appears in the share sheet for YouTube videos and for pages in Safari.

Reviewing material several times with gaps in between, instead of in a single long session. Reviews spaced over days produce better long-term retention than the same amount of study done at once.

A document that organizes material for learning: the key concepts, their definitions and the main takeaways. Study Guide is one of SumAI's five summary styles.

The finding that being tested on material improves later memory of it more than studying it again. In a well-known 2006 experiment by Roediger and Karpicke, the advantage of testing showed up on tests taken two days and one week later.

Software that reads written text aloud in a synthetic voice. SumAI's Listen feature reads summaries aloud at 0.75x to 2x speed.

A marker for a position in a video, written as minutes and seconds, such as 18:40. In SumAI, timestamps in key moments, Ask AI answers and the transcript can be tapped to jump to that point.

Short for "too long; didn't read". It has come to mean a very brief summary of something longer, usually a sentence or a paragraph. In SumAI, TL;DR is the shortest of the five summary styles: one paragraph with just the point.

The written text of everything said in a video or recording, usually with timestamps. On YouTube, a transcript is available when a video has captions.