Spanish SER Rules, Conjugations, and Stem-Changing Verbs

When do you use SER for description?

Used for physical descriptions, size, color, and essential qualities (e.g., Él es alto).

When do you use SER for occupation?

Used for jobs, professions, and trades (e.g., Ella es médica).

When do you use SER for characteristics?

Used for personality traits and inherent nature (e.g., Somos simpáticos).

When do you use SER for time and date?

Used for telling time, days of the week, dates, and seasons (e.g., Son las tres / Hoy es lunes).

When do you use SER for origin?

Used to state nationality or where someone/something is from (e.g., Soy de México).

When do you use SER for relationships?

Used for family relationships, friendships, and ownership/possession (e.g., Es mi hermano / El libro es de Ana).

Conjugate SER (yo, present):

soy

Conjugate SER (tú, present):

eres

Conjugate SER (él/ella/usted, present):

es

Conjugate SER (nosotros/nosotras, present):

somos

Conjugate SER (vosotros/vosotras, present):

sois

Conjugate SER (ellos/ellas/ustedes, present):

son

What is the 'Boot' Rule?

Stem-changing verbs change in all present-tense forms EXCEPT Nosotros and Vosotros.

What is the Infinitive Rule?

Verbs NEVER stem-change when left in the infinitive form (e.g., después de 'querer').

What is the -IR Vowel Pattern for -erir, -ertir, -entir?

These -IR endings almost always undergo an (e -> ie) stem change.

What is the -IR Vowel Pattern for -edir, -egir, -eguir, -ervir?

These -IR endings almost always undergo an (e -> i) stem change.

Conjugate querer (yo, present):

quiero

Conjugate empezar (yo, present):

empiezo

Conjugate pensar (yo, present):

pienso

Conjugate entender (yo, present):

entiendo

Conjugate preferir (yo, present):

prefiero

Conjugate cerrar (yo, present):

cierro

Conjugate dormir (yo, present):

duermo

Conjugate poder (yo, present):

puedo

Conjugate volver (yo, present):

vuelvo