Here are four rules of thumb for converting English words in to Spanish.
- Words ending in -ible or -able often stay the same.
- Change words ending in -ent and -ant to end in -ente and -ante respectively.
- Change words ending in -tion to end in -ción.
- Change words ending in -ical to end in -ico (or -ica if feminine).
These are only rules of thumb. There are exceptions. For example, two exceptions to the third rule are that the Spanish word for translation is traducción and the word for explanation is explicación. But these rules hold quite often.
Related post: Xylophones and zebras part II: Learning Spanish