Lingua Latina Per Se Illustrata. Capitulum Secundum. Casus Genetivus.

2. Consider the English word /dɔg/.
(Forget about spelling for a moment.)

3. You know exactly what it means,
and in English the sound-cluster /dɔg/
has only one meaning.

4. But what about /dɔgz/?

5. If you hear someone say, “These two beasts are /dɔgz/”,
you know instinctively from context
that it’s a plural subject...

6. ...while, if you hear
“This is that /dɔgz/ bowl”,
you know, also from context, that the same sound shows that the bowl
belongs to a singular dog. Same sounds, different meaning.

7. We distinguish these in writing (<dogs> and <dog’s>)
but the sound is the same.
The difference comes about in the context.

8. The one we spell <dog’s>
is in the Genitive Case
(Casu Genetívo).

9. Now we’ll get this case in Latin.
And these first examples will in fact
follow the exact same pattern as English.