sì wéi
the four social bonds: propriety, justice, integrity and honor
see 禮義廉恥|礼义廉耻[li3 yi4 lian2 chi3]
the four directions
the four limbs (Chinese medicine)
four-dimensional
sì wéi kōng jiān
four-dimensional space (math.)
sì wéi shí kōng
four-dimensional space-time (in relativity)