A word is all of its forms

The dictionary form is the one you need least

Open a dictionary and you get one form per word: grad, city. Open your mouth and you almost never need that form. I live in the city takes another one. The centre of the city takes a third. I like this city takes a fourth. In a language with cases a noun has up to fourteen forms, and the dictionary form is one of them, used in one grammatical role, and no more common than the rest.

A verb is worse. Videti, to see, has more than thirty forms across its persons, numbers, tenses and moods. The infinitive you find in the dictionary is the one that never appears in I see you, did you see, we will see or look.

Vocabulary apps count words. A learner who "knows 2,000 words" in the dictionary-form sense knows 2,000 things that they will have to change, on the fly, every time they use one. That is not vocabulary. It is a list of vocabulary to be learned.

Regular is not the same as free

Most forms follow a pattern, and the pattern is a rule you can learn once. That helps with understanding. It does not help with speed. When you are saying where you live, there is no time to run the rule: masculine, ends in a consonant, locative, so add -u. The form has to be there, whole, the way went is there for a native English speaker who has never thought about the past tense of go.

That is what fluency in the endings feels like: not a fast rule, but no rule at all. And it comes from the same place all fluency comes from, which is producing the form many times, spaced over weeks, until it stops being assembled and starts being retrieved.

Then there are the ones that follow nothing

Every language has a core of high-frequency words whose forms are not built from the dictionary form at all. In English: go, went, gone; is, was, been; child, children. In Serbian the word for a person is čovek and the word for people is ljudi, a different word altogether. A child is dete and children are deca, which then declines as if it were a singular feminine noun. The verb ići, to go, is idem in the present and išao in the past.

These are not rare curiosities. They are the most used words in the language, exactly because words that are used constantly resist being regularised. A learner who has the rules and not these forms is fluent in the parts of the language that do not come up.

How the course treats a form

Every form of every word is its own item. It has its own level from 1 to 10, its own place in the repetition schedule and its own history of right and wrong answers. The locative of grad can be at level 8, rock solid, while the genitive plural is at level 2 and coming back tomorrow. The word as a whole is not what is scheduled; the forms are.

They are never drilled as a table. A form comes due and you meet it inside a sentence you have to write from scratch, in the role that calls for it. If you produce the wrong ending, the check marks that word, names the rule, and halves the level of that form and of that rule. The other forms of the same word are untouched, because you did not get them wrong.

When a word is introduced, you see all of it at once: the picture, the voice, the translation, and every form, so you know from the first day what you are taking on. The table is there to look at, not to memorise. The memorising happens in the sentences, one form at a time, on the day each one is due.

What this changes

It changes what "I know this word" means. In a flashcard deck it means you can produce the dictionary form. Here it means every form you have met is above a certain level, tested in use, and the ones that are not are the ones coming back. You can see the level of every word and every rule you know, at any time, and the ones still low are the ones on their way.

And it changes what a mistake costs. Get the genitive of one noun wrong and you have not lost the noun. You have lost one form, for one day, and tomorrow you will write it again.