0 to become fashionable or popular: --
1 to understand, especially after a long time: --
He doesn't take hints very easily, but he'll catch on (to what you're saying) eventually.
2 to become fashionable or popular: --
Why did the electronic gadget catch on so fast?
3 to understand: --
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Можем да го завършим стъпка по стъпка, колкото и дълъг да е пътят и не може да бъде завършен, колкото и кратък да е пътят, ако дори не маркирате отпечатъка си.