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Verbos con cambio ortográfico i > y (pretérito indefinido)

Stem-changing Spanish i>y verbs in the simple past tense

Spanish verbs ending in -uir undergo a change when they are conjugated in the simple past.
The -i- changes to -y- but it only affects the 3rd person singular and plural

For example: 
Construir (to build) → construyó/ construyeron
Note: Oir (to hear) is another verb affected by this change despite not ending in -uir.

To see a list of verbs affected by this irregularity go to List of Spanish irregular -uir verbs (i > y) in the present and past tenses.
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