Learn Spanish (Latin America): Mi hermano quiere leer diecinueve libros en un mes. - My brother wants to read nineteen books in a month.

It comes from combining diez y nueve (ten and nine). When numbers 16 through 19 are squeezed into a single word, the z in diez changes to a c, and the y (and) changes to an i. So, diez y nueve becomes diecinueve.

Why does diecinueve not have an accent mark when dieciséis does?

Dieciséis (16) needs an accent mark to keep the spoken stress on the correct syllable when the words are combined. However, diecinueve (19) naturally puts the spoken stress on the second-to-last syllable (nue). This follows standard Spanish pronunciation rules, so no extra written accent mark is needed!

Why is the second verb leer instead of lee?

In Spanish, when two verbs are used together to express a single idea (like "wants to read"), only the first verb is conjugated (changed to match the subject). Since we already changed the first verb to quiere (he wants), the second verb stays in its base, unchanged form: leer (to read).

Why does the sentence use un instead of uno for "a month"?