踩(cǎi) - to step on, to tread on in Mandarin

踩 (cǎi) is the everyday verb for putting your foot down on something: a brake pedal, a puddle, somebody else's toes. It is physical and concrete, and it almost always takes a direct object.

Note that no preposition comes between the verb and what you tread on. English needs one - step ON the brake, tread ON the grass - but Chinese does not: 踩刹车, 踩草地. Adding 在 or 到 changes the meaning to landing on a specific spot, as in 踩到我的脚.

The near-synonym 踏 (tà) is the more formal, written cousin, and it carries a sense of treading deliberately or setting foot somewhere. If you are talking about accidentally standing on the cat, 踩 is the word you want.