You study fifty words one evening. The next day you remember thirty, a week later ten. By the end of the month most of the list looks unfamiliar again. Most people blame their own laziness for this. In fact it is exactly how memory is supposed to behave.
Forgetting is the rule, not a fault
Your brain meets thousands of new facts every day and cannot keep them all. So it applies a filter: anything not encountered again gets deleted. Learn a word once and never see it again, and your brain marks it as unnecessary. The problem is not you — it is the review schedule.
That means the real question is not "how many times should I repeat this" but "when should I repeat this". Reviewing the same word ten times in one day helps far less than reviewing it once a day for ten days. The spacing matters more than the count.
The logic behind spaced repetition
Spaced repetition rests on a single idea: see the word again just before you would have forgotten it. Reviewing a word you recall instantly wastes time; reviewing one you have completely lost means learning it from scratch. The productive moment sits precisely between those two.
In practice the schedule looks like this: the day you learn the word, the next day, three days later, a week later, two weeks later, a month later. Every successful recall stretches the interval; every failure sends it back to the start. Software does that arithmetic for you — your only job is to open it daily.
Recognising is not remembering
The most common mistake is reading a list and concluding "I know these". Seeing a word next to its meaning is recognition; producing that same word from nothing while speaking is production. The gap between them is wide, and someone who only trains recognition stalls in exams and conversation alike.
The fix is simple: cover the meaning, try to recall it yourself first, then look. That one extra second of effort does more for retention than reading the same list five times over. It is called active recall, and it is the single most efficient move in learning.
Never learn a word alone
A word memorised in isolation falls out at the first opportunity. Instead of "reach = to arrive at", learn "to reach an agreement". A word inside a sentence gives you two things: something for memory to hold on to, and a demonstration of how the word is actually used. This is precisely why people who know many words still cannot build sentences.
For the same reason, write one sentence with every new word — a sentence from your own life. For "book", not the dictionary example but a sentence about the book you are currently reading. Personal context makes recall noticeably easier.
How many words are enough
Don't let the numbers frighten you. Most everyday conversation turns on a small core: the first 1,000 words cover roughly eighty percent of daily speech, and the first 3,000 give you the backbone of most texts. C1 needs something like 8,000 — but the core has to be solid before you head there.
So piling on new words is not always the right move. Being able to use the five hundred words you already know while speaking is worth more than recognising two thousand.
Give the weak words more time
Not every word on a list is equally hard. Everyone has a stubborn group that keeps slipping away. A good system flags those and shows them to you more often; a bad one walks the list front to back in the same order and spends most of your time on words you already own.
How to start today
Fifteen minutes a day, every day, beats an hour or two once a week by a wide margin. Open your word cards, cover the meaning and try to recall, keep the ones you missed aside, and start the next day with those.
If you don't know where to begin, take the free placement test first; the result comes on the CEFR scale and tells you which vocabulary band you are in. Then work through the word list for the language you're learning, and say every word out loud inside a sentence.