あのシャツは汚い。学校に行く前に洗う必要があります。

that (someone or something distant from both speaker and listener, or situation unfamiliar to both speaker and listener)

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

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

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

school

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

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

ago; before (some event); previously; (minutes) to (the hour); in front (of); before (e.g. the house); head (of a line); front (e.g. of a bus); fore part; in the presence of; helping; portion; privates; private parts

to wash; to investigate

necessary; needed; essential; indispensable; necessity; need; requirement

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about