From the clues left at the scene, the detective inferred that the crime had been premeditated.

inferred 是动词 infer 的过去式，infer 由前缀 in-（表示"向内"）和词根 fer（来自拉丁语 ferre，意思是"携带"）组成，字面意思是"把信息带入（思维中）"，引申为"根据已有信息得出结论"，即"推断"。