Rana vs. sapo
In Spanish, the words rana and sapo refer to different types of tailless amphibians, much like the distinction between a frog and a toad in English. While they belong to the same animal order, they have distinct physical traits, habitats, and even cultural slang meanings.
Rana
The word rana translates to frog. It is used to describe amphibians that typically have smooth, moist skin, long hind legs designed for leaping, and usually live in or near water.
La rana saltó desde la roca hasta el estanque.
(The frog jumped from the rock into the pond.)
Escuchamos el canto de una rana durante toda la noche.
(We heard the song of a frog all night long.)
Esa rana tiene colores muy brillantes porque es venenosa.
(That frog has very bright colors because it is poisonous.)
Los niños atraparon una rana verde en el jardín húmedo.
(The children caught a green frog in the damp garden.)
La princesa besó a la rana esperando que se convirtiera en príncipe.
(The princess kissed the frog hoping it would turn into a prince.)
Sapo
The word sapo translates to toad. It describes amphibians with dry, rough, or warty skin, shorter legs better suited for walking or short hops, and a preference for living on dry land. Additionally, in many Spanish-speaking countries, sapo is used as slang to describe a snitch, an informant, or a very nosy person.
Encontré un sapo enorme escondido debajo de las hojas secas.
(I found a huge toad hiding under the dry leaves.)
Mi abuela dice que tocar un sapo te dará verrugas en las manos.
(My grandmother says that touching a toad will give you warts on your hands.)
El sapo camina lentamente por el sendero de tierra.
(The toad walks slowly down the dirt path.)
No le cuentes tus secretos porque él es un sapo.
(Do not tell him your secrets because he is a snitch.)
El perro se asustó cuando el sapo infló su cuerpo como defensa.
(The dog got scared when the toad puffed up its body as a defense.)
Summary
To summarize, you should use rana when talking about a smooth, water-loving frog, and sapo when talking about a bumpy, land-dwelling toad. You can also use sapo in casual conversation to label someone as a snitch or a busybody.