[FFranco]

Spanish is an inflected language, isn’t it?

[SumProVita]

Even Old English was moderately inflected. ;-)

[Verginius Rufus]

Spanish has preserved more inflections than English, especially with the verb, but it's not very inflected compared to Latin. Where Latin had different forms for nominative, genitive, dative, accusative, ablative, and sometimes for the vocative, Spanish has a single form (only changing to indicate the plural, like English does).

The general tendency among Indo-European languages is to lose inflections over time--none of the Romance languages is as highly inflected as Latin, English is much simpler than Anglo-Saxon, Modern Greek is simpler than classical Greek, etc. The Slavic languages have kept more inflections than some of the other European branches. I don't know if that's true in the Indo-Iranian languages.