Your sentence
Le+escribo+una+carta.
Words in this sentence
le
to him, for him; dative of él; to her, for her; dative of ella; to it, for it; dative of ello; to you, for you (formal); dative of usted; you (formal); accusative of usted; him; accusative of él; it; accusative of ello; her; accusative of ella; to them, for them (singular); dative of elle; to them, for them (singular); accusative of elle
Pronoun
escribir
to write (to form letters, words or symbols on a surface in order to communicate); to write (to) someone (a letter, etc.); to write someone something; to write (to be the author of (a book, article, poem, etc.)); to write (to be an author); to type (on a phone or computer keyboard); to text; to chat regularly with someone on social media
Verb