During the pandemic, many small businesses suffered greatly from reduced commercial activity.

businesses 是名词 business 的复数形式，business 指"商业、企业、生意"。这里指具体的"商业机构"或"企业实体"。 suffered 是动词 suffer 的过去式，suffer 意思是"遭受、经历(困难或痛苦)"，常与 from 搭配使用表示"因...而遭受损失/痛苦"。 reduced 是动词 reduce 的过去分词形式，reduce 意思是"减少、降低"，这里 reduced commercial activity 指"商业活动减少"的情况。