waterproof and watertight

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Senior Member
Chinese - Mandarin
Dear native speakers,

Is there any difference between the words "waterproof" and "watertight"?

When it comes to light, e.g. a type of material that light cannot easily pass through, can I use "lightproof" or "light-tight"? If not, is there a word for the meaning?

  • RCA86

    Senior Member
    British English
    As far as I understand, waterproof and watertight are the same. If there is a difference, it's probably not really an important one. As an observation though, clothes and shoes tend to say 'waterproof' on them. I've heard 'watertight' used more in the sense of to make something watertight. If you have a tent, which has a hole in it, you might 'make it watertight', so the water doesn't get in.

    You can't really use that construction with 'light' I'm afraid. We call glass 'transparent', since you can see through it (therefore light passes through it). Transparent also has a more figurative meaning which you can look up. If something is not transparent (meaning that light can not pass through it), we tend to call it 'opaque', but you can use 'non-transparent' if you want.

    There is probably a scientific word for this, but I'm not sure what it is. And no, your questions were good, but maybe nobody noticed the thread, and it dropped onto the second page.


    Senior Member
    (San Francisco) English
    I usually use 'waterproof' for clothing and 'watertight' for containers. 'Waterproof' often gets used as a synonym for "water resistant" (or the two words are used for two different grades of raincoats/boots/etc.). To me, 'watertight' implies that the item will be carrying liquid or carrying something dry but immersed in liquid.

    'Lightproof' is fine. I have not seen 'light-tight'. 'Transparent' means that you can see through something. 'Translucent' means that light passes through it (but you can't see through it--think of frosted glass).


    Lapsed Moderator
    English-Ireland (top end)
    Waterproof - something that resists water. Water cannot penetrate it.
    So my coat is waterproof. I can walk about in the rain and not get wet.
    It is not watertight. It has lots of holes for bits of me to get through, it has button-holes and lots of little breather holes

    Watertight - something that can contain water is watertight. My boots are watertight. They are also waterproof, of course.


    Senior Member
    (San Francisco) English
    Strangely, the free dictionary lists both 'lightproof' and 'light-tight' as valid.


    I've never heard either of them in real life.
    Most people don't have a need to lightproof anything. If you look up information on constructing your own darkroom or pot growing operation, you'll find plenty of references to lightproof black plastic sheeting and things like that.
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