シャツを替えなさい。とても汚いよ。

shirt (underwear); undershirt; singlet; shirt (outerwear, esp. dress shirt)

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 replace; to exchange; to interchange; to substitute

to do

very; awfully; exceedingly; (not) at all; by no means; simply (cannot)

dirty; filthy; foul; unclean; disordered; messy; untidy; poor (e.g. handwriting); indecent (language, etc.); dirty; vulgar; coarse; dastardly; mean; base; underhanded; stingy; greedy

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!