bit 侧重指微小，一点点，小碎片。
piece 最普通用词，多指从整体上分割下来的东西，可大可小。
sheet 侧重指平整很薄的一张或一片。
slice 多指切得很薄的一片食物。
fragment 指破裂的，不完整的，不可完整的碎片。
scrap 侧重指废弃的零碎之物。
参考例句
1. The snow sheeted down last night. 昨天夜里下起了鹅毛大雪。
2. When send your quotation sheet, please do not forget to send sample of the quote goods. 当寄送报价单时，请贵公司不要忘记将报价货物的样品也一并寄来。
3. For a shortcut to inserting a sheet from another file, choose Insert > Sheet from file from the menu bar. 从另一个文档插入一个表的快捷方式，是从菜单栏选择插入>来自文件的工作表。
英英解释
n.
1. any broad thin expanse or surface
2. used for writing or printing
3. bed linen consisting of a large rectangular piece of cotton or linen cloth; used in pairs
4. (mathematics) an unbounded two-dimensional shape
5. newspaper with half-size pages
6. a flat artifact that is thin relative to its length and width
7. (nautical) a line (rope or chain) that regulates the angle at which a sail is set in relation to the
8. a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing v v.
1. come down as if in sheets
2. cover with a sheet, as if by wrapping
