"The children write letters."
Translation:Les enfants écrivent des lettres.
"des lettres" is the plural of "une lettre".
"des" is THE plural indefinite article in French that does not exist in English.
"des" is the plural of "un" or "une".
In addition, if you open Tips and Notes of the Basic1 unit (at the bottom of the main lesson page and via a button at the top of every sentence page), you will find full explanations on this matter.
In English "some" is optional to mean "an undefined number of things": they write (some = more than just one) letters.
In French, determiners are required as a general rule.
In this case, "des" is required as the plural indefinite article:
- ils écrivent une lettre (singular) => ils écrivent des lettres (plural)
Note that in English articles "a/an" do not have a plural form.
An -s is added to the verb stem in various cases:
- with pronoun "tu", always
- with pronoun "je", only for verbs of 2nd and 3rd groups (infinitives in -ir or -re)
"écrivent" is the complete form of verb écrire in 3rd person plural.
Conjugation of verb écrire in indicative present: j'écris, tu écris, il/elle/on écrit, nous écrivons, vous écrivez, ils/elles écrivent.