It's two reasons for teenagers to wear mask, One is to stop them infecting other people but also there is one element of protection against other kids who are also chattering away as they go along that crowded corridor.

Source of info: https://youtu.be/KD44ynY6Wts?t=207

Can you explain why they use against here? wearing the mask is a protection of element that support others. So why against?

  • 2
    Your clip only starts at the end of the sentence, but "There are two reasons for teenagers to wear masks" would seem more likely. Why against? Because you protect yourself against something that could harm you - here, catching the virus from other children.. Commented Mar 3, 2021 at 16:06

1 Answer 1


Protect implies that there is a threat of some kind. We use from or against to express what that threat is.

The threat is really Covid, or infection by Covid:

The mask protects us against infection/Covid.

But by metonymy we can also refer to the source of the infection as the threat:

The mask protects us against people with Covid.

and specifically

The mask protects us against children who are chattering, and therefore, if infected, breathing out the virus.

By the way It's for two reasons for ... is not idiomatic English. We can say It's for two reasons. as the reply to a question, but if we are going to qualify it with a purpose (for students to wear masks), only There are two reasons is idiomatc.

  • 1
    Colin, another upvote. it could be from, too.
    – Lambie
    Commented Mar 3, 2021 at 17:09

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