While only the Portuguese verb partir (to break) is used as the example for the 3rd conjugation, the rules contained here pertain to all regular verbs ending in -ir except irregular verbs ending in -ir. View the list of singular and plural subject pronouns and the notations used here before proceeding.

IMPERSONAL (to break)
PERSONAL INFINITIVE (me to break)
PARTICIPLES & GERUND (broken, breaking)

INDICATIVE MOOD (SIMPLE)
PRESENT INDICATIVE (I break)
IMPERFECT INDICATIVE (I was breaking/I used to break)
PRETERIT INDICATIVE (I broke)
PLUPERFECT INDICATIVE (I had broken)
SIMPLE FUTURE INDICATIVE (I will break/I shall break)
COMPOUND FUTURE INDICATIVE (I will break/I shall break)

INDICATIVE MOOD (COMPOUND)
PRESENT PERFECT INDICATIVE (I have broken/I have been breaking)
PLUPERFECT INDICATIVE (I had broken)
FUTURE PERFECT INDICATIVE (I will have broken/I shall have broken)

SUBJUNCTIVE MOOD (SIMPLE)
(The SUBJUNCTIVE occurs in the DEPENDENT CLAUSE of a sentence)
PRESENT SUBJUNCTIVE (I may break)
IMPERFECT SUBJUNCTIVE (I might break)
FUTURE SUBJUNCTIVE (if I were to break/if I would break/if I should break/if I may break/if I might break)

SUBJUNCTIVE MOOD (COMPOUND)
(The SUBJUNCTIVE occurs in the DEPENDENT CLAUSE of a sentence)
PRESENT PERFECT SUBJUNCTIVE (I may have broken)
PLUPERFECT SUBJUNCTIVE (I might have broken)
FUTURE PERFECT SUBJUNCTIVE (if I were to break/if I would break/if I should have broken/if I may have broken/if I might have broken)

CONDITIONAL MOOD
(The Conditional is called the preterit future in Portuguese)
SIMPLE (I would break/I should break)
COMPOUND (I would have broken/I should have broken)

IMPERATIVE MOOD
AFFIRMATIVE FORM (break thou/you/we/ye/they)
NEGATIVE FORM (don't break thou/you/we/ye/they)