Tierra vs. mundo
In Spanish, both tierra and mundo can be translated as earth or world, but they are not interchangeable. Tierra primarily refers to the physical planet, the ground or soil, and land. In contrast, mundo refers to the world in a more abstract or societal sense, encompassing humanity, its cultures, and its systems.
Tierra
A1This word refers to the planet Earth as a physical and astronomical body, the ground or soil we walk on, or a specific piece of land, country, or homeland.
La Tierra es el tercer planeta del sistema solar.
(The Earth is the third planet in the solar system.)
El jardinero necesita más tierra para las macetas.
(The gardener needs more soil for the pots.)
Después de la lluvia, el camino era de tierra y lodo.
(After the rain, the path was dirt and mud.)
Mis abuelos nacieron en esta tierra.
(My grandparents were born in this land.)
Compraron una hectárea de tierra para cultivar.
(They bought a hectare of land to cultivate.)
El avión está a punto de tomar tierra.
(The plane is about to land (touch ground).)
Mundo
A1This word refers to the world as a concept of society, humanity, and all its countries and cultures. It can also describe a specific sphere of life, a field of interest, or a figurative, vast concept.
Quiero viajar y conocer todo el mundo.
(I want to travel and get to know the whole world.)
La tecnología ha cambiado el mundo moderno.
(Technology has changed the modern world.)
El mundo de la moda es muy competitivo.
(The world of fashion is very competitive.)
Para un padre, sus hijos son su mundo.
(For a father, his children are his world.)
Hay un mundo de diferencia entre vivir en la ciudad y en el campo.
(There is a world of difference between living in the city and in the countryside.)
Todo el mundo estaba feliz en la fiesta.
(Everyone (the whole world) was happy at the party.)
Summary
In essence, the key difference is physical vs. societal. Use tierra when you are talking about the physical planet, the ground beneath your feet, or a specific territory. Use mundo when you are referring to the global community, human society, a specific conceptual realm like the business world, or the idea of everyone.