1. Mail or postal service that follows a standard schedule and delivery pattern, typically slower than express or priority mail
I sent the documents by regular mail instead of overnight delivery.
Enviei os documentos por correspondência regular em vez de entrega noturna.
2. Ongoing communication or exchange of letters between two or more parties on a consistent basis
They maintained regular correspondence throughout their years apart.
Mantiveram correspondência regular durante todos os anos afastados.