English grammar: palabras invariables

In, on, at:

Explicación in, on, at de lugar


In, on, at, for places

In, on, at, places 2

Prepositions of Place: at, in, on

Generalmente, se utiliza:

IN para un espacio delimitado: “Dentro de”, “en (interior)”:

• Espacios cerrados: in my room, in the living room, etc.
• Dentro de objetos: in the box, in the book, etc.
• Lugares con límites definidos: in the park, in the football pitch, etc.
• Ciudades y países: in London, in Germany, etc.
• Esquina dentro de una habitación: in the corner.

 ON para una superficie: “Sobre”, “encima de":

• Sobre superficies: on the table, on the beach, etc.
• Direcciones: on the right, on the left, etc.
• Partes del cuerpo: on the arm, on the head, etc.
• Medios de transporte: on a bus, on a plane, etc.
• Esquina exterior como la de un edificio: on the corner.
• Haciendo referencia a una página específica de un libro o revista: on the page 347.

AT para un punto determinado: “En”, “junto a”, “al lado de”

• Lugares comunes: at home, at school, etc.
• Lugares específicos: At Natural History museum, at the Cambridge University, etc.
• Direcciones y domicilios: at 2393 Colon Square
• Sitios concretos de un establecimiento: At the door, at the window, etc.
• Citas y acontecimientos: at the party, at the meeting, etc.
• Posiciones: at the top/bottom, at the front/back, etc.

at	in	on
POINT	ENCLOSED SPACE	SURFACE
at the corner	in the garden	on the wall
at the bus stop	in London	on the ceiling
at the door	in France	on the door
at the top of the page	in a box	on the cover
at the end of the road	in my pocket	on the floor
at the entrance	in my wallet	on the carpet
at the crossroads	in a building	on the menu
at the front desk	in a car	on a page

Por supuesto, este uso no sigue unas normas estrictas en todos los casos: no hay una regla definida o fórmula, y la mejor forma de aprenderlo es con la práctica. 
Además, hay casos concretos, expresiones, como:

at home, at work (at school, at university, at college), at the bottom, at the side.

in a lift, in the newspaper, in the sky.

on a horse, on the radio (on the Television), on the left (on the right, on the way)