Every dense book has a moment where you hit a name, a phrase, a word used in a sense that died out two centuries ago, and you have a choice. Stop and go look it up, breaking whatever spell the page had on you. Or keep reading past it, and lose a little of what the writer meant. Summa exists so you don't have to choose.
Reading without leaving the page
The oldest annotated books had a kind of fractal structure. Everything you needed to understand a passage lived in the same place as the passage itself. Glossed manuscripts carried their commentary in the margins and between the lines. A page of the Talmud wraps a few lines of text in centuries of argument. The reference and the reading were never apart.
Summa is an attempt to bring that back. The details come to you instead of you going to them, so you never lose your focus or leave what you are reading. When you want to know more, you hover and peek at what it says, then keep going. Nothing to look up, no tab to open, no spell broken.
What it does
Summa sits in your menu bar and reads along with you. Hover a highlighted word or phrase in Kindle, in a PDF, in a browser tab, in whatever app you're actually reading in, and Summa shows you what it means: a Wikipedia reference, a short editorial gloss for the allusions that don't reduce to a single link, or a plain definition for a word that's fallen out of common use. Nothing to import, no separate reading app to switch into. It works on the screen you already have open.
Why it exists
The best annotated editions (the Norton Critical Editions, the heavily footnoted classics) treat a reader as someone who wants to catch everything, not just the plot. That's rare outside of a classroom, and it doesn't exist at all for the book you downloaded last night or the article a friend sent you. Summa is an attempt to put that kind of editorial attention underneath anything on your screen, quietly, without turning the page into a wall of footnotes.
How it decides what to annotate
Summa is opinionated about restraint. It's built to skip common words, generic phrases, and anything a reader would already know, and to spend its attention on the handful of things per page that are actually worth a reader's pause: a biblical or classical allusion, a piece of period context, a callback to something earlier in the same book, a word whose meaning has drifted. Getting the selection right, annotating less but annotating the things that matter, is most of the work.
Try it
Summa is free, notarized for macOS, and still early. The demos on the home page show it running on a few chapters of classic literature. Hover any highlighted word to see it in action before you download.