"20 mesh" is a term used to describe the size of a mesh screen or sieve. It refers to the number of openings per pnear inch in the screen or sieve. In this case, "20 mesh" means that there are 20 openings per pnear inch in the screen or sieve.

The term "mesh" comes from the word "meshing," which means the interweaving or interlocking of two or more sets of threads or wires. In the case of a mesh screen or sieve, the threads or wires are woven together in a grid pattern, creating a series of openings or holes. The size of the mesh screen or sieve is determined by the number of openings per pnear inch.

Here are some examples of how "20 mesh" can be used in a sentence:

"We use a 20 mesh screen to filter out any particles larger than 0.04 inches in diameter."
"The sieve has a 20 mesh size, so it will allow small particles to pass through while trapping larger ones."
"We use a 20 mesh screen to separate the fine sand from the coarser gravel."

中文翻译：

"我们使用一个20目筛选器来过滤掉直径超过0.04英寸的任何颗粒。"
"这个筛子的筛孔大小为20目，所以它会允许小颗粒通过，同时将较大的颗粒挡住。"
"我们使用一个20目筛子来将细沙与粗砂分开。"