Spanish stem-changing verbs: e to ie and o to ue

The vowel that breaks

Regular verbs keep their stem still: «hablo», «como», «bebo», «vivo». Now look at «quiero» and «quieres», at «cuesta» and «cuestan», at «no entiendo». The endings are the ordinary ones: -o for yo, -es or -as for tú, -a or -e for él and ella. What changed is inside the verb. An e has become ie; an o has become ue. It happens in the syllable your voice leans on: in «quiero» you lean on quie-, in «cuesta» on cues-. When the stress lands on that vowel, the vowel breaks.

• Quiero un café

  I want a coffee

• Hoy no quiero café

  Today I don't want coffee

• No entiendo

  I don't understand

• La camisa cuesta mucho

  The shirt costs a lot

• ¿Cuánto cuesta?

  how much does it cost?

• No entiendo español

  I don't understand Spanish

• No entiendo, pero hablo un poco

  I don't understand, but I speak a little

Pued-, and endings you already own

The verb is «poder», to be able to. Every singular form starts pued-: the o broke into ue when the stress landed on it, exactly as in «cuesta». What goes on the end is the regular -er set: «puedo», «puedes», «puede». Whatever follows is the second verb in its plain infinitive: «puedo cocinar», «puedes nadar», «puede leer». The first verb bends to agree with the person; the second one just sits there.

• Poder

  to be able to, can

• Hoy no puedo cocinar

  I can't cook today

• No puedo cocinar hoy

  I can't cook today

• Ana puede cantar

  Ana can sing

• Mi hermana puede leer

  My sister can read

• Puedes comer aquí

  You can eat here

• Ana puede nadar

  Ana can swim

• Quiero bailar

  I want to dance

• Puedo hablar español

  I can speak Spanish

«entiendo» was a verb all along

«no entiendo» is two words, and the second one is a verb. Its infinitive is «entender», to understand. It is an -er verb, so by the ordinary rule it should hold its stem still like «comer» and «beber». It does not: the e in the middle breaks into ie, and out comes «entiendo». Same break as «quiero». The endings are the plain ones, -o for yo and -e for él and ella, so «entiende» is he or she understands.

• Mi hermano entiende el español

  my brother understands Spanish

• Mi hermana entiende un poco

  my sister understands a little

• Yo no entiendo la película

  I don't understand the movie

• Mi hermano entiende, pero yo no entiendo

  My brother understands, but I don't understand

• Ahora entiendo

  now I understand

• No entiendo, pero quiero entender

  I don't understand, but I want to understand

The same break, a second time

«dormir» is to sleep. It is an -ir verb, so the endings are the ones «vivir» takes: «vivo», «vive». Now line the stems up. «vivir» keeps its stem exactly as it is. «dormir» does not: the o breaks open into ue, and you get «duermo» and «duerme». It is the same break as «poder» → «puedo» and «costar» → «cuesta». One verb doing it is an exception; several is a rule, and the rule is that the vowel breaks when it is the stressed one, which in yo, tú and él/ella it always is.

• Duermo tarde

  I sleep late

• Mi hermano duerme tarde

  my brother sleeps late

• El gato duerme mucho, pero el perro no duerme

  The cat sleeps a lot, but the dog doesn't sleep

• El sábado y el domingo

  on Saturday and on Sunday

• Hoy duermo un poco

  today I sleep a little

• El perro duerme en la cama

  the dog sleeps on the bed

• No trabajo el domingo, duermo tarde

  I don't work on Sunday, I sleep late

Third verb, same crack

«empezar», to begin, does it too: «empieza». Three verbs, three splits, all in the same place, the syllable your voice leans on: «entiende» (e → ie), «duerme» (o → ue), «empieza» (e → ie). Now look at the END of «empieza». It is -a, the same -a that finishes «habla», «estudia» and «trabaja». That is the whole deal: the endings stay exactly as they are, and one vowel in the middle of the word breaks. Nothing else changes.

• Quiero empezar temprano

  I want to begin early

• La película empieza temprano

  the movie begins early

• La película empieza tarde

  The movie begins late

• Estudio en la escuela

  I study at the school

• El trabajo empieza temprano

  work begins early

• Ana no entiende la película

  Ana doesn't understand the movie

• La escuela empieza temprano, pero la película empieza tarde

  school begins early, but the movie begins late

The column you never finished

Read down the he/she column: «puede», can; «duerme», sleeps; «entiende», understands; «empieza», begins. Every one of them cracked in the middle, and every one of them ends the ordinary way. «quiero», «quieres», «quiere» and «cuesta», «cuestan» belong to the same family. What a dictionary lists them under is the infinitive: «querer», to want; «costar», to cost; «poder»; «dormir»; «entender»; «empezar». Look at the middle of those: no ie, no ue, just the flat vowel. The break happens when the verb is put on a person, and never in the infinitive.

• Ana quiere un café

  Ana wants a coffee

• Ana quiere un té

  Ana wants a tea

• Diego duerme tarde

  Diego sleeps late

• Querer

  to want

• ¿Cuánto puede costar?

  how much can it cost?

• ¿Cuánto cuesta esta camisa?

  how much does this shirt cost?

• Los zapatos cuestan mucho

  the shoes cost a lot

• Ana quiere comprar esta camisa, pero cuesta mucho

  Ana wants to buy this shirt, but it costs a lot

Check yourself

Questions from the course. Pick an answer to check it; nothing is saved.

1. 1.Three of these are the plain stem plus its ending. One has an extra vowel wedged inside it. Which one?

   hablocomoquierovivo

2. 2.Which one means 'it costs'?

   costacostascuestacostan