Oración vs. plegaria vs. rezo
The Spanish words 'oración', 'plegaria', and 'rezo' all refer to the act of prayer or communicating with God. However, they are used in slightly different contexts and carry subtle differences in connotation.
Oración
'Oración' is the most generic term for prayer. It can be used in any context where one is communicating with a higher power, but it's especially linked to a structured form, like a ritual or litany.
Vamos a recitar una oración antes de comer.
(We are going to recite a prayer before we eat.)
La oración del Padre Nuestro es conocida por todos los cristianos.
(The Lord's Prayer is known by all Christians.)
Plegaria
'Plegaria' carries a more emotional, intimate tone. It is often used to express an earnest desire or plea in a more personal and intense way.
Escuchó mi plegaria y me ayudó en mi momento más difícil.
(He listened to my plea and helped me in my hardest time.)
Envío una plegaria al cielo por tu salud.
(I send up a prayer to heaven for your health.)
Rezo
'Rezo' refers specifically to the act of praying and can also imply repetition. It is often associated with regular, ritualistic types of prayers.
Realizo el rezo de la mañana todos los días.
(I perform the morning prayer every day.)
El rezo del rosario es una práctica católica común.
(The praying of the rosary is a common Catholic practice.)
Summary
'Oración', 'plegaria', and 'rezo' all refer to the act of prayer, but differ in connotation: 'oración' typically refers to a structured form of prayer, 'plegaria' has an emotional, heartfelt connotation expressing personal pleas, and 'rezo' refers to regular, ritualistic types of prayers.