Todo vs. entero
In Spanish, both todo and entero can translate to whole or entire, but they are not always interchangeable. The key difference is that todo refers to all the parts of a whole, while entero refers to a single, complete and unbroken unit.
Todo
A1This word means all or every. It refers to the entirety of a group, a quantity, or a period of time, emphasizing the inclusion of every single component or member. It is very versatile and can function as an adjective, pronoun, or adverb.
Leí todo el libro en una noche.
(I read the whole book in one night.)
Todos los niños jugaban en el parque.
(All the children were playing in the park.)
Ella trabaja todo el día sin descansar.
(She works all day without resting.)
Limpiamos toda la casa antes de la fiesta.
(We cleaned the whole house before the party.)
Todo está bajo control.
(Everything is under control.)
El coche está todo mojado por la lluvia.
(The car is all wet from the rain.)
Entero
A2This word means entire, whole, or complete. It emphasizes that an object is a single, undivided, and unbroken unit. It is most often used as an adjective for things that could potentially be cut, divided, or portioned.
Se comió el pastel entero él solo.
(He ate the entire cake by himself.)
Para la receta necesito un pollo entero.
(For the recipe, I need a whole chicken.)
El pueblo entero salió a celebrar.
(The entire town came out to celebrate.)
Pasamos el día entero en la playa.
(We spent the entire day at the beach.)
El edificio entero fue evacuado.
(The entire building was evacuated.)
Siete es un número entero.
(Seven is a whole number (an integer).)
Summary
Use todo to mean all or every, when referring to all the individual parts of a whole or all members of a group (e.g., todos los amigos - all the friends). Use entero to mean entire or complete, when emphasizing that a single item is whole and unbroken, especially if it could be divided (e.g., un pastel entero - an entire cake). While todo el día and el día entero are often interchangeable, entero adds a stronger emphasis on the object as a single, indivisible block.