Hold one object in mind: a net with small holes. Air goes through it; mosquitoes do not. Sand goes through it; large stones stay on top. That one action — let most things pass, hold back the few that matter — is what nearly every use of screening is doing, with a different load each time. Put a crowd of healthy people through it and the few early illnesses stay on the net. Put bags and passengers through it and the few risky ones are stopped. One sense stands slightly apart, because it uses the other kind of screen: the flat surface a film is thrown onto.
The word is screen + -ing, so it names either the screen material itself or the act of using a screen. That is why one form covers a roll of mesh, the act of sieving, and the checking of people.
按字面拆開，screening 就是 screen 加上 -ing。所以它可以指網子這個材料本身，也可以指「拿網子去過一遍」這個動作。同一個形式能同時當一捲紗網、一道篩分工序、一次對人的檢查，原因就在這裡。
Wiktionary entry for 'screening' supplied in this packet (kaikki:3f6f69a190036ae4:1265390192): 'From screen + -ing.' This is a surface analysis of the modern word, not a full history of screen.
Three branches
網子本身，跟把材料過網
這一支就是核心畫面本人：一張網，跟拿這張網去分東西。看得見、摸得到，其他用法都是從這裡借畫面的。
noun · B2
Net-like material with very small holes, made of wire or plastic, that is fitted over a window or door so that air can come through but insects cannot; also the material itself, bought by the roll or the metre.
紗網
把人或東西整批過一次篩
網子沒變，倒進去的東西變成了人、行李、履歷。一樣是大量進來、多數通過、少數被留下來細看。
noun · B2
Medical tests given to large numbers of people who feel well, so that a particular disease can be found early — before the people being tested have noticed anything wrong.
篩檢
另一塊 screen：銀幕
這一支跟濾網那張圖接不太上，因為它用的是 screen 的另一個面向：不是讓東西穿過的網，而是讓影像停在上面的那塊平面。這是概念上的分家，不是在主張兩個字的來歷不同——本包沒有這方面的詞源證據。
noun · B2
An occasion when a film or a television programme is shown to an audience — in a cinema, at a festival, at a school or library, or at a private event for invited guests.
放映（場次）
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
screeningnoun/ˈskɹiːnɪŋ/
Mesh material that is used to screen (as in a "screen door").
The examination and treatment of a material to detect and remove unwanted fractions by passing it through a screen (sieve).
Material removed by such a process; refuse left after screening sand, coal, ashes, etc.
The examination of any material or persons to detect problems through any of various testing, checking, or filtering processes, as
medicinesciencesThe examination of any material or persons to detect problems through any of various testing, checking, or filtering processes, as:
businessThe examination of any material or persons to detect problems through any of various testing, checking, or filtering processes, as:
A test or method used for this purpose.
The showing of a film, typically by projecting it on a screen.
ball-gamesgameshobbiesShielding.
ball-gamesgameshobbiesAction done by the serving team to prevent the opposing team from seeing the server and the flight path of the ball.
這個拼法也被記錄為下列字的變化形：
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。