This is the 6478th most frequent Japanese word.
セルヒオ
"セルヒオ" is the Japanese katakana transliteration of the Spanish name "Sergio."
Here, 'セルヒオ' is used as a proper noun, referring to the name of the individual, Sergio.
セルヒオさんは日本語を勉強しています。
Sergio is studying Japanese.
In this case, 'セルヒオ' is used in the possessive form to indicate ownership, connected with 'の'.
セルヒオの家はとても広いです。
Sergio's house is very spacious.
Here, 'セルヒオ' represents the sender of the letter, highlighting the context of interaction.