Desatar vs. desanudar vs. soltar
When learning how to talk about untying or releasing items in Spanish, you will frequently encounter the verbs desatar, desanudar, and soltar. While they can all relate to freeing something from a binding or knot, they have distinct everyday uses ranging from general untying, specifically undoing a stubborn knot, to simply releasing or letting go of an object.
Desatar
The verb desatar is the most common and versatile word for to untie. It is the standard choice for untying shoelaces, ribbons, or standard knots, and can also be used figuratively to mean to unleash or to trigger an event.
Tengo que desatar mis zapatos antes de quitármelos.
(I have to untie my shoes before taking them off.)
Ella intentó desatar la cinta del regalo con mucho cuidado.
(She tried to untie the ribbon of the gift very carefully.)
El mago logró desatar las cuerdas en cuestión de segundos.
(The magician managed to untie the ropes in a matter of seconds.)
Sus comentarios amenazan con desatar una crisis política.
(His comments threaten to unleash a political crisis.)
El viento fuerte ayudó a desatar la lona de la tienda de campaña.
(The strong wind helped to untie the canvas of the tent.)
Desanudar
The verb desanudar is highly specific and literally translates to un-knot. It is used when the focus is on the physical and sometimes tedious action of undoing a stubborn, tight, or complex knot, rather than just untying a simple bow.
Me tomó diez minutos desanudar este hilo de pescar.
(It took me ten minutes to unknot this fishing line.)
El marinero experto sabe muy bien cómo desanudar las cuerdas mojadas.
(The expert sailor knows very well how to undo the knots in wet ropes.)
Tienes que desanudar la bolsa de plástico para sacar las verduras.
(You have to unknot the plastic bag to take out the vegetables.)
Sus dedos temblaban al intentar desanudar la soga.
(His fingers trembled while trying to undo the knot in the rope.)
Es casi imposible desanudar estos cables de auriculares sin romperlos.
(It is almost impossible to unknot these headphone cables without breaking them.)
Soltar
The verb soltar broadly translates to to let go, to release, or to loosen. When applied to knots, shoelaces, or ropes, soltar implies slackening or physically releasing your grip on them, rather than the meticulous mechanical action of taking a knot apart.
Por favor, tienes que soltar la cuerda para que el bote pueda avanzar.
(Please, you have to let go of the rope so the boat can move forward.)
El perro se va a escapar si decides soltar la correa.
(The dog is going to escape if you decide to release the leash.)
El nudo estaba tan flojo que se terminó por soltar solo.
(The knot was so loose that it ended up coming undone by itself.)
Necesito soltar el cinturón después de comer tanta comida.
(I need to loosen my belt after eating so much food.)
Al soltar los globos, todos los niños miraron hacia el cielo.
(Upon releasing the balloons, all the children looked up at the sky.)
Summary
In summary, use desatar as your everyday, general word for untying shoelaces or bindings. Choose desanudar when you want to emphasize the specific action of undoing a tight or difficult knot. Finally, use soltar when you need to express the broader action of releasing, letting go of, or loosening something.