conjugate : verb :: decline : noun

Declining is what you do to a noun to make it fit its role in a sentence. By "role," I specifically mean a case. Depending on how a noun is used in a sentence, one alters its declination to reflect the appropriate case, usually by selecting the appropriate ending. The number of cases that require different declinations vary by language. English, for example, does not decline. In each of the following sentences, the same form of the word "dog" is used, despite the fact that it has a different case in each one.

  1. The dog is stupid.
  2. I see the dog.
  3. I talk about the dog.
  4. It is cold to the dog.
  5. I eat the dog's ass.
  6. I work by means of my dog.

(I apologize for the somewhat contrived nonsensical sentences. Unfortunately, my vocabulary is rather weak.)

However, here are those sentences translated to Russian (and then transliterated, roughly, into a non-Cyrillic character set). Note how the ending on "sabaka" changes in each sentence.

  1. Sabaka -- gloopaya.
  2. Ya veeju sabakoo.
  3. Ya govaryu o sabakye.
  4. Sabakye xolodno.
  5. Ya yem jopoo sabakee.
  6. Ya rabotoo sabakoy.

The above sentences illustrate the six case declinations in Russian:

  1. Nominative: the subject of a sentence.
  2. Accusative: the object of a verb.
  3. Prepositional: the subject of a preposition.
  4. Dative: the indirect object.
  5. Genitive: possession.
  6. Instrumental: being used as a tool or means.

Please note that all languages have cases. However, only some languages recognize this fact by way of declension. If you've learned nothing else from this write-up, you've learned how to say "I eat the dog's ass" in Russian.

I understand Latin has an even more complex case system, but I feel ill-equipped to comment on it.