It's the Way You Say It
There are three main types of inflections in Spanish:
1) Nominal inflection - This group is inflected in regard to GENDER and NUMBER.
The endings are -o for the masculine singular and -a and for the feminine singular and -os and -as respectively for plurals.
2) Verbal inflection - This group is inflected in regard to PERSON and NUMBER.
The endings for verbs are first person singular of the present indicative -o, second person singular -s, third person singular -a or -e, first person plural -amos or -emos or -imos, second person plural -áis or -éis or -ís, and third person plural -an or -en.
This group is also inflected in regard to TENSE and MOOD.
The endings are -aba (preterit imperfect indicative, first conjugation); -ía (preterit imperfect indicative, second conjugation); -ra, -se (preterit pluperfect subjunctive); -ría (conditional); -re (future subjunctive); -e (present subjunctive, first conjugation); and -a (present subjunctive, second and third conjugations).
3) Verbal-Nominal inflections - This is made up of the infinitive ending -ar or -er- or -ir, the gerund -ando or -endo, and the past participle -do.