Difference between Froth & Foam?

Question

What is the difference between froth & foam? Is there any difference?

Can someone please give some example sentences to understand the both words better?

Answer 1

They are basically the same thing in regular usage.

The milk in my coffee is frothy. The coffee has froth on the top.

The milk in my coffee is foamy. The coffee has foam on the top.

The ocean was foaming from the storm. or frothy or foamy.

Those are positive in meaning.

The difference resides mostly in technical or medical usage:

• Spray the foam into the space between the two strips of wood and then press them together.

  Foam there is the form of a particular substance: a foam as opposed to a liquid. So, glue could be in the form of a foam, rather than liquid.

• The man had been poisoned and froth had come out of his mouth.

  Froth is used to refer to the spittle that comes out of a person's mouth, usually, if they are sick or have been poisoned, for example.

Froth and foam are also used to describe anger: He was so angry he was frothing or foaming at the mouth. [spittle was coming out of his mouth].

Answer 2

For somebody who isn't a native English speaker, I would say that simply referring to a dictionary is a mostly pointless exercise in this case.

I normally use Merriam-Webster, so I'll continue to do so here. I'll also (mostly) limit my response to the nouns. (Note that Oxford has some similar issues.)

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I'll start with its definition of froth:

1 a : bubbles formed in or on a liquid : FOAM
b : a foamy slaver sometimes accompanying disease or exhaustion
2 : something resembling froth (as in being unsubstantial, worthless, or light and airy)

• Sense 1a starts off well—but then gives foam as a synonym. If you're trying to distinguish between the two, this isn't helpful.

• Sense 1b seems clear. But after I present the definition of foam, you'll see that it's actually not so simple.

• I have a pet peeve against dictionaries that use a word they are defining in its definition. Here, saying that froth is "something that resembles froth" is mostly useless for anybody who wants to know what froth itself looks like. But the rest of the definition is useful: "as in being unsubstantial, worthless, or light and airy."

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Here is Merriam-Webster's definition of foam:

1 : a light frothy mass of fine bubbles formed in or on the surface of a liquid or from a liquid: such as
a : a frothy mass formed in salivating or sweating
b : a stabilized froth produced chemically or mechanically and used especially in fighting oil fires
c : a material in a lightweight cellular form resulting from introduction of gas bubbles during manufacture
2 : SEA
3 : something resembling foam

• Sense 1, 1a, and 1b all use froth or its adjective as part of the definition for foam. Again, this is not helpful if you're trying to tell the difference between the two.
• Sense 1a says the same thing as sense 1b of froth when it comes to sweating (something produced by exhaustion from exercise).
• Sense 1c is clear.
• Sense 2 is interesting but also confusing. To understand it, Oxford's definition of foam is actually more helpful: "(the foam) literary The sea. ‘Venus rising from the foam’.
• Sense 3 isn't really helpful at all and, unlike sense 2 of froth, doesn't include anything extra.

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So, what are we left with?

Aside from some specific uses, both froth and foam seems to have no clear guidance that would allow you to distinguish between them.

Sometimes, this is fine. Many words have synonyms that can be used in their place. In such cases, it's simply a matter of choosing the word that sounds best to you; other people may choose a different word because the other word sounds best to them.

I have some general guidelines in my personal use:

• If it's dispensed from a can, I call it a foam. This seems to follow sense 1b of the definition of foam, despite its use of the adjective frothy. So, shaving cream is also referred to as shaving foam (rather than shaving froth).

• If a liquid is agitated by hand, it's more often a froth than a foam.

• Personally, I think of foam as being thicker and denser, whereas I'll consider froth to be lighter and airier. (While I wouldn't describe whipped cream with either word, if I were forced to, I'd likely use foam rather than froth—despite the method of its creation.)

• Cappuccinos and other milk-based drinks can have either froth or foam. However, a machine for producing this is called a milk frother, not normally a milk foamer.

Some of these are simply examples of idiomatic use. They aren't necessarily explained by a specific dictionary entry, nor does one necessarily follow the same "rule" as another.