You look up the same word for the fifth time and it still won't stick. That experience is so common in language learning that many people assume they are just bad at vocabulary. They usually aren't. They are using a method that doesn't match how memory works, and a few changes to how you capture and review words make a large difference.

In short

New words fade quickly if you only see them once or twice. Reviewing each word just as it starts to fade is the most reliable fix.
Make cards that ask you to produce the word, not just recognise it.
Keep it to one meaning per card, and add a short example sentence when a word has no clear stand-alone meaning.
Add words from material you actually meet, not only from lists.
Start with a small number of new words a day; the workload builds up faster than it feels like it will.
A routine you can keep during a busy week beats a heroic one you drop.

Why words slip away

Meeting a word in a lesson and understanding it is the beginning of learning it, not the end. Memory follows the pattern Ebbinghaus measured in the 1880s: steep loss soon after learning, then slower loss (the forgetting curve). A word that felt obvious on Monday may be unavailable by Thursday.

The remedy is not to look at the word more often in one sitting. It is to meet it again at well-chosen moments, with some effort each time. That is spaced repetition, applied to vocabulary.

Start with the right words

Not every word deserves a card. A few filters help.

Frequency. Words you will meet often reward the effort quickest. A word you may never see again is a poor investment.
Relevance. Words connected to your life - your work, your hobbies, the people you talk to - tend to stay.
What you've actually met. A word you saw in an article this morning is in a much better position than one pulled from a random list, because you already have a memory of the context.

Be wary of very long lists taken out of nowhere. They are easy to collect and hard to learn.

One meaning per card

A word with three senses is three things to learn. If you put all three on a single card, you can recall two and still feel you knew the card, and the third never gets its turn. Splitting the senses gives each its own schedule.

This is the vocabulary version of a general rule: each card should ask for one small thing (how to write good flashcards).

Put the word in a sentence

A bare translation is the weakest kind of vocabulary card. It strips away how the word behaves.

Compare these two backs for the same card:

key
key - "Ich finde meinen Schlüssel nicht." (I can't find my key.)

The second gives you grammar, word order and a scene to attach the word to. Prefer sentences you found yourself or that mean something to you; they are easier to remember than invented ones.

Practise producing, not only recognising

Recognising a word when you see it is easier than producing it when you need it. If your goal is to speak or write, your cards should ask you to produce.

Recognition card: front is the foreign word, back is the meaning in your language.
Production card: front is the meaning, a short description or an image, and back is the foreign word.

You do not have to make both for every word. Make production cards for the words you want to use actively, and recognition cards for words you only need to understand when reading. This is active recall in practice: the effort of retrieving the word is what builds the memory.

Use images where they fit

For concrete nouns, a picture on the front can be better than a translation, because it skips your first language entirely. A photo of a key leads you straight to the word for key. In Cirello, images can go on either side of a card and open in a zoomable lightbox, so a photo or a screenshot from something you were reading is a valid card.

Learn words from what you read

Words you meet in context come with a source. If you are reading a book or an article in your target language, you can capture a word with a note on where it came from. In Cirello, a card can prompt from a resource, such as a book, plus an instruction like "page 40", so you can review the word where you met it. The approach is described in more detail on the page about remembering what you read.

Getting words in quickly

Language courses and your own notes already produce word lists. The tedious part is typing each pair into an app. Cirello supports pasting a list of front::back pairs so the whole set becomes cards in one pass, and duplicate detection means re-pasting an expanded list will not double your deck. See bulk-importing flashcards. Cirello does not include audio or ready-made language courses, so you bring your own words.

A caution: easy bulk import makes it tempting to add a hundred words at once. Resist that. Choose the words you want to learn first, then paste them.

How many new words a day

Each new word will return many times over the coming weeks, so intake translates directly into future workload. Start with a modest number - a handful rather than dozens - and watch your daily queue for a couple of weeks before changing it. How many flashcards should you review per day explains how to reason about it.

A routine that survives real life

Here is a simple pattern that holds up during a busy week.

Capture as you go. When you meet an unknown word that passes your filters, note it. Don't build cards in the moment unless it is quick.
Batch the cards. Once a day or a few times a week, turn the notes into cards, splitting meanings and adding a sentence.
Review daily, briefly. A few minutes. Do what is due, answer before you reveal, and grade honestly.
Don't catch up in one go. If you skip days, work through the queue in shorter sessions instead of one marathon.
Prune. If a word has turned out to be rarely useful, remove it. A selective deck is more pleasant to review.

Cirello's scheduler, FSRS-6 retrained nightly on your own history, brings each word back near the point you would forget it and shows only what is due. If you blank on a word, it is offered again in the same session. The streak is drawn as a plant that fades if you miss a day instead of resetting, so there is no penalty for the busy week. For more on how the scheduling works, see what FSRS is.

Beyond flashcards

Flashcards are a way to keep words from fading, not a way to learn a language on their own. You still need listening, reading, speaking and writing, which give words meaning and give you reasons to retrieve them. Think of flashcards as the maintenance layer: they make sure the words you've met are still there when you need them.

To go deeper on the use case, see the page for language learning.

How to memorize vocabulary in a new language