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Both "el primero" and "la primera" are forms of "primero", which is often translated as "first". Learn more about "primero" below.
primero(
pree
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meh
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roh
)An adjective is a word that describes a noun (e.g., the big dog).
1. (position)
a. first
Los países se enumeran en la primera fila de la tabla.The countries are listed in the first row of the table.
2. (in time)
3. (principal)
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
This means that the noun can be masculine or feminine, depending on the gender of the noun it refers to (e.g., el doctor, la doctora).
a. the best
Era el primero en matemáticas en séptimo grado.I was the best in mathematics in seventh grade.