Note: mecer, to rock, is an exception to this rule. It is
conjugated by rule 3. below like vencer.
2. Verbs ending in -ducir make the same changes as does conocer
in the Present Indicative, Present Subjunctive, and Imperative, and
in addition they are irregular throughout the Preterit Indicative
and in both forms of the Imperfect Subjunctive.
TRADUCIR, to translate
Present Indicative Present Subjunctive
traduzco traducimos traduzca traduzcamos
traduces traducís traduzcas traduzcáis
traduce traducen traduzca traduzcan
Preterit Imperfect Subjunctive
traduje tradujimos tradujera tradujéramos
tradujiste tradujisteis tradujeras tradujerais
tradujo tradujeron tradujera tradujeran
Imperative
----- traduzcamos
traduce traducid
traduzca traduzcan
Some verbs of this type are:
conducirse producir reproducir traducir
3. Verbs ending in -cer or -cir preceded by a consonant change c
to z before a or o. This change occurs in the first person singular
of the Present Indicative and in all persons of the Present Subjunctive.
It also occurs in the third person singular and first and third persons
plural of the Imperative.
VENCER, to conquer
Present Indicative Present Subjunctive
venzo vencemos venza venzamos
vences vencéis venzas venzáis
vence vencen venza venzan
Imperative
----- venzamos
vence venced
venza venzan
Some verbs of this type are:
vencer vencer mecer*
RADICAL CHANGING VERBS
1. CLASS I: verbs ending in -ar and -er change o to ue and e to ie
when the stem is stressed at that syllable. This change occurs in the
singular and third person plural of the Present Indicative and Present
Subjunctive and in the second and third persons singular and third
person plural of the Imperative. Some are irregular in the Past
Participle, as in volver--vuelto
CONTAR, to tell, to relate
Present Indicative Present Subjunctive
cuento contamos cuente contemos
cuentas contáis cuentes contéis
cuenta cuentan cuente cuenten
Imperative
------ contemos
cuenta contad
cuente cuenten
2. CLASS II: verbs ending in -ir change o to ue and e to ie when
the stem is stressed. They also change o to u before a stressed
-a, and e to i before -ie or -ió. The first two changes occur in the
singular and third person plural of the Present Indicative and Present
Subjunctive and in the second and third persons singular and third
person plural of the Imperative. The second two changes occur in the
third persons singular and plural of the Preterit, in the Present
Participle, and in all six persons (and in both forms) of the Imperfect
Subjunctive.
SENTIR, to feel, to regret
Present Participle: sintiendo
Present Indicative Present Subjunctive
siento sentimos sienta sintamos
sientes sentís sientas sintáis
siente sienten sienta sientan
Preterit Imperfect Subjunctive
sentí sentimos sintiera sintiéramos
sentiste sentisteis sintieras sintierais
sintió sintieron sintiera sintieran
3. CLASS III: verbs ending in -ir change e to i before stem is
stressed, before a stressed -a, and before an -ie or -ió. This change
occurs in the singular and third person plural of the Present Indicative and in all persons Present Subjunctive, in the second and third persons
singular and first and third persons plural of the Imperative, in the
third person singular and plural of the Preterit, in the Present
Participle, and in all persons (and in both forms) of the Imperfect
Subjunctive.
PEDIR, to ask, to request
Present Participle: pidiendo
Present Indicative Present Subjunctive
pido pedimos pida pidamos
pides pedís pidas pidáis
pide piden pida pidan
Preterit Imperfect Subjunctive
pedí pedimos pidiera pidiéramos
pediste pedisteis pidieras pidierais
pidió pidieron pidiera pidieran
Imperative
---- pidamos
pide pedid
pida pidan
NOTE: Many verbs have more than one change, as in the case of verbs that have both radical changes and orthographic changes. In these cases, follow the rules for first one change, then overlay the changes called
for by the rules for the other changes.
I have tried to include the verb data for all irregular verbs, so
if you need to know anything about them, you'll have print them out and
study them separately, as I know of no rules that will satisfy all cases.