¡Ojo!: When Spaniards want to say ‘watch out!’ or ‘be careful!’, they say ¡ojo!. 

There’s also the idiom andarse con ojo, which implies watching your back or treading carefully. And to emphasise this even further, you can say andarse con cien ojos/mil ojos, to walk with 100 eyes or 1,000 eyes!

¡Ojo! El suelo está mojado. 

Watch out! The floor is wet.

Ándate con ojo con Jaime porque tiene fama de traidor. 

Watch your back with Jaime because he’s got a reputation for being a backstabber.

No pegar ojo: To not sleep a wink, used when you’ve been unable to sleep.

Me he pasado toda la noche en vela, no he pegado ojo. 

I’ve been up all night, I didn’t sleep a wink.

Costar un ojo de la cara: The same as saying in English ‘to cost an arm and a leg’, in the sense that something is very expensive or costly.  You can also use valer instead of costar, both mean ‘to cost’.

Pagarle los estudios a mi hijo me ha costado un ojo de la cara. 

Paying for my son’s studies has cost me an arm and a leg.

Mirar por el rabillo del ojo: To look sideways or out of the corner of your eye. 

No se inmutó pero no dejaba de mirarle por el rabillo del ojo.

He didn’t bat an eyelid but he wouldn’t stop looking at him out of the corner of her eye.

Tener ojo de lince: If you’ve got a very keen and observant eye, in English you say you have an eagle eye, but in Spanish you’d say you have a lynx eye. 

María tiene ojo de lince, no se le escapa ninguna. 

María has got a real eagle eye, she doesn’t miss a thing.

En un abrir y cerrar de ojos: Literally meaning in the time it takes to open or close your eyes, this expression is not too dissimilar to its English equivalent – in the blink of an eye – when something happens very quickly. 

En un abrir y cerrar de ojos el ladrón había robado las joyas.

In the blink of an eye the thief had stolen the jewels. 

Mirar con buenos ojos: To look upon someone or something favourably, to have a soft spot for something/someone or to have a positive outlook on something. 

El jefe te mira con buenos ojos aunque llegues tarde al trabajo.

The boss has a soft spot for you even if you’re late for work.

Ser el ojito derecho: If you’re someone’s ‘little right eye’, it means you’re the teacher’s pet. It doesn’t always have to apply to being a teacher’s favourite pupil as it can be used when referring to someone else’s preferred person. There’s also the expression la niña de sus ojos (the apple of somebody’s eye).

Margarita es el ojito derecho de la profe. 

Margarita is the teacher’s pet. 

A ojo: If you do something a ojo, it means you do it blindly or by eye or by guesswork, without knowing exactly.

Estoy calculando cuánta gente hay en la sala a ojo. 

I’m making a rough guess of how many people there are in the room.

Echarle un ojo a: ‘To throw an eye’ in Spanish means to check something out, to have a look at, to look over. It can also mean to keep an eye on or watch over someone or something.

Échale un ojo a este cuadro que he pintado. 

Have a look at this painting I’ve painted. 

Mal de ojo: Evil eye.

La gitana le echó un mal de ojo por no comprarle el romero. 

The gipsy woman cast an evil eye on her for not buying her rosemary. 

No tener ojos en la cara: ‘To not have eyes on one’s face’ actually means to not see something that’s obvious or to not pay attention or care to something. 

¿Cómo qué se ha perdido el niño? ¿Es que no tienes ojos en la cara?

What do you mean the boy is lost? Did you fall asleep at the wheel?

No quitar ojo: To stare intently at something or someone without fail. If it’s with desire, there’s also the expression comerse con los ojos a algo/alguien, to eat something or someone with the eyes.

La rubia no te quita ojo, chaval. 

The blonde girl won’t stop looking at you, man.