Learn vocabulary from conversations — reviewing right before you forget (FSRS)
You looked a word up mid-meeting. You understood it. A week later it's gone. That isn't a discipline problem — it's a timing one, and it's the real reason it's so hard to learn vocabulary from conversations. The fix isn't more effort; it's meeting each word again at the right moment.
You can finish a whole vocabulary book and never hear those words in a real meeting — yet the one term a colleague used last Tuesday sticks without any effort. That gap is worth understanding. So before any pitch, here's how memory actually behaves with words you meet in conversation, and why review timing matters more than review volume.
I spent six months building Hiroi, a solo iOS app that fuses live translation with learning, and this "how do words actually stick" question is the one I kept circling. I wrote earlier about what to do when you can't follow English meetings; when I said the real work happens after the meeting, this is what I meant.
Why it's easier to learn vocabulary from conversations than from wordlists
A word on a list is a dot floating in empty space. It has a meaning, but no hook — nothing about who said it, when, or why it mattered.
A word you caught in a real meeting arrives with the whole scene attached: the client, the tense pause, your colleague's face as they chose it. That single term is now tied to several cues at once. Psychologists call this elaborative encoding, but you don't need the label — the more hooks a word has, the easier it is to pull back later. It's also why words from your own work keep returning: same client, same field, the vocabulary repeats. Learning the words you're actually going to meet again is simply the most efficient order to learn them in.
The forgetting curve: timing beats volume
Why do we forget? The classic picture is Hermann Ebbinghaus's forgetting curve: without review, most of what you learn today falls away within a few days. It's a steep slope.
Here's the trap most people fall into — reviewing a lot, all at once, every day. Looking at a word you still remember is mostly wasted effort. Reviewing one you've completely forgotten is nearly relearning it from scratch. What actually works is recalling a word once, right as you're about to forget it. Each time you do, the slope gets gentler and the gap to the next review stretches out. So the thing that matters isn't how many times you review — it's when. A few reviews aimed at the right moment beat a big daily pile.
The catch: that "about to forget" moment is different for every word. Tracking it by hand, word by word, never lasts.
How a spaced repetition app targets the moment you'd forget (FSRS)
That per-word timing is exactly what a spaced repetition app works out for you. The scheduler many now use is FSRS (Free Spaced Repetition Scheduler).
FSRS estimates a forgetting curve for each item and schedules the next review right around the point where you'd otherwise lose it. Words you know well get pushed far out; shaky ones come back soon. The result is high retention from surprisingly few reviews — and you never have to decide when to study. The review comes to you, right as you're about to forget. It's a quiet mechanism, but the payoff compounds: same effort, more retained, because it's aimed correctly. It's a far kinder way to remember new words than brute-force repetition.
Keep fewer words, not more
One counterintuitive rule: don't hoard.
A conversation offers endless words you don't know. But if you funnel all of them into a review queue, what you've really built is a growing pile of guilt — and that's what kills the habit. A handful of words per meeting is plenty. The only filter you need is: will I use this again? Does it help the next me? Keep it tight and each word gets richer context and an easier path back. Catch a few and turn them into a line — that goes much further than catching everything and dropping it all.
Dots into a line — catch, learn, meet again
Everything above works with a paper notebook and any off-the-shelf spaced repetition app. The friction is doing all of it — following captions live, building review cards afterward, and noticing when a word comes back — across separate tools. That rarely lasts. Hiroi folds it into one loop:
- Catch: after a meeting, save a word you want to keep with one tap.
- Learn: saved words go into an FSRS deck; review arrives right before you'd forget.
- Meet again: when a learned word resurfaces in a real conversation, the app quietly tells you.
That "met it again" moment is the dots becoming a line. And from the day's caught words, a small hand-drawn card is made — not a stat or a streak, just a quiet record of the words you met that day.
Translation itself is only getting cheaper. What I think remains once translation is free is the learning — and this is my attempt to help people learn vocabulary from conversations without bolting on yet another app. Hiroi never records audio; transcripts and your deck stay on your device. There's no subscription — the first hour is free, then prepaid time packs (from ¥600), and time you buy never expires. If that resonates, take a look at hiroi.app.
May the word you catch today come back just as you're forgetting it — and, one day, come out as your own.