know-how (the knowledge and skill to be able to do something correctly)

Used other than figuratively or idiomatically: see vai, saber. / who knows (a rhetorical question asked to show that the asker neither knows the answer nor who might know it) / who knows (asked to express the idea that anything is possible)

knowledge is power

(idiomatic) to know very well

(rude) I don't care

sabre saw