メアリーは階段をおりて台所へ行った。

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

stairs; stairway; staircase

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to descend (e.g. a mountain); to go down; to come down; to alight (e.g. from bus); to get off; to disembark; to dismount; to step down; to retire; to give up; to quit; to be granted; to be issued; to be given; to form (of frost, dew, mist, etc.); to be passed (from the body; e.g. of a roundworm)

kitchen; financial situation

indicates direction or goal (e.g. "to")

to go; to move (in a direction or towards a specific location); to head (towards); to be transported (towards); to reach; to proceed; to take place; to pass through; to come and go; to walk; to die; to pass away; to do (in a specific way); to stream; to flow; to continue; to have an orgasm; to come; to cum; to trip; to get high; to have a drug-induced hallucination