Verb Spelling & Vowel Quality

• Drop consonant c then add qu before e;
• Drop consonant g then add gu before e;
• Drop the cedilla, but keep consonant c before e.

Examples:

 Imperativo afirmativo of verb ficar

Imperativo afirmativo of verb pegar

Imperativo afirmativo of verb caçar

Verbs of the 2nd and 3rd conjugations:

• Add a cedilla to c before a and o;
• Drop consonant g then add j before a and o;
• Drop the gu then add g before a and o.

Examples:

 Imperativo afirmativo of verb crescer

Imperativo afirmativo of verb fingir

Imperativo afirmativo of verb erguer

The spelling rules apply to all verb tenses in which vowels e, a and o follow the consonants stated above. Imperativo afirmativo is just an example.

 
Changes in Vowel Quality

Vowels e and o may change vowel quality along the presente do indicativo, presente do subjuntivo, imperativo afirmativo and imperativo negativo in certain environments.

Closed vowels e and o that precede the infinitive ending -ar become open vowels (e as in get and o as in hot) in the persons that have been highlighted:

Remember:

Vowels e and o are always closed in the infinitive.

Vowels e and o are always closed in the persons nós and vós of all verb tenses.

Vowels e and o are closed in all persons of the other verb tenses.

These guidelines apply to verbs of the three conjugations.

There aren't changes in vowel quality (the vowels are closed) along conjugations when:

• Vowels e and o are followed by m, n, lh or nh;

• Vowels e and o are followed by i;

• Vowel e is followed by x, ch and j.

• Verbs in -oar

Examples

These rules cover most verbs in the language; an important exception, however, is verb chegar (verb to arrive), of which all verb tenses, in all persons, have a closed e:

Vowels e and o that precede the infinitive ending -er are closed vowels  (e as in get and o as in hot) before m, n, lh and nh:

Otherwise, verbs follow the pattern of verb escrever:

open vowel

closed vowel

Two important exceptions are the irregular verbs querer and poder, which present the following vowel pronunciation in the presente do indicativo, presente do subjuntivo, imperativo afirmativo and imperativo negativo:

open vowel

closed vowel

Since most irregular verbs fall under the 3rd conjugation, it is hard to set a rule for them: you'd better consult a dictionary to avoid mistakes. Nevertheless, a lot of frequent vowel changes in verbs follow the patterns of verbs aderir and dormir:

e turns into i in certain persons and tenses

o turns into u in certain persons and tenses

Summary:

Regardless of the verb conjugation, the following rules are always applicable:

Vowels e and o are always closed in the infinitive.

Vowels e and o are always closed in the persons nós and vós of all verb tenses.

Vowels e and o are closed in persons of all verb tenses other than presente do indicativo, presente do subjuntivo, imperativo negativo and imperativo negativo.