The German articles table, and the thing you need before it
The whole chart, definite and indefinite, sits in four rows. It is small enough to copy out in a minute. What it cannot tell you is whether the noun in front of you is a der, a die or a das, and until you know that, every singular column is shut to you. The plural column is the one part you can read without it. That is why plurals feel easy and everything else does not.
Read across a row and you have a case. Read down a column and you have a gender. The definite table holds sixteen cells and only six different words, so nobody loses marks here because the table is long. They lose them because they picked the wrong column.
That is the part worth being blunt about. To put a noun in the accusative you have to know its gender first, and the gender is not in the sentence anywhere. It is a property of the word, which you either carry or you do not. So this table is the second problem. The first one is that Tisch is der, Tür is die and Fenster is das, and nothing below will tell you which.
Which case a sentence calls for is decided by the verb or the preposition in front of the noun, and that is a different subject from this one. This page prints the forms. The rest of this site is about the column.
The definite article: the
| Case | Masculine | Feminine | Neuter | Plural |
|---|---|---|---|---|
| Nominative | der | die | das | die |
| Accusative | den | die | das | die |
| Dative | dem | der | dem | den |
| Genitive | des | der | des | der |
Two places the noun moves too. In the dative plural it takes an -n wherever it can: die Kinder becomes den Kindern. In the genitive, masculine and neuter nouns take -(e)s: des Mannes, des Kindes.
The indefinite article: a, and its plural
| Case | Masculine | Feminine | Neuter | Plural |
|---|---|---|---|---|
| Nominative | ein | eine | ein | keine |
| Accusative | einen | eine | ein | keine |
| Dative | einem | einer | einem | keinen |
| Genitive | eines | einer | eines | keiner |
Ein has no plural, because "a" has no plural to have. The plural column is kein, the negative, which carries the endings the missing form would have taken and is what a plural row of this table can honestly show. Mein, dein and sein decline the same way.
Start with the column, not the row
Every column above is a gender, and the word itself tells you which one far more often than most teaching admits. German builds nouns out of suffixes that carry a gender, so the ending is not a hint about the word, it is the reason the word has that article. One for each column:
Thirty endings do this kind of work, each one with a reliability measured against a finite exam syllabus rather than asserted about the language at large. Learn the endings and the column stops being a guess, and only then does the table above become usable.