Froth, foam, lather or suds?

I know this topic is unlikely to pique any native speaker's curiosity, but bear with me, I am trying to learn the difference between froth, foam, lather and suds.

I feel these terms are not always interchangeable even though they mean more or less the same. There isn't anything called shaving froth. Yet, I can't explain clearly the difference between froth, foam, lather and suds.

I would appreciate if someone could enlighten me.

(Edit) ODO definitions:

1. Froth – a mass of small bubbles in liquid caused by agitation, fermentation, or salivating.
2. Foam – a mass of small bubbles formed on or in liquid, typically by agitation or fermentation.
3. Lather – a frothy white mass of bubbles produced by soap, washing powder, etc. when mixed with water.
4. Suds – froth made from soap and water.

What follows may be regional to the mid-western US version of English.

"Lather" and "suds" are reserved for mixtures of soap and water. "Suds" usually implies larger bubbles whereas "lather" has small or no bubbles. You will find "suds" in your laundry wash tub but not "lather." Your shampoo bottle instructs you to "lather, rinse, repeat," but the soapy substance on your head can be described as either "lather" or "suds." Shaving cream makes "lather," which is rarely, if ever, described as "suds."

"Foam" usually implies a certain permanence to the material whereas the bubbles found in "froth" usually, but not always, dissipate fairly quickly. "Foam" also implies larger bubbles than "froth." Whipped cream can be described as "frothy," but without having noticeable air bubbles it would probably not be described as "foamy." "Frothy" can also be used to describe churning water, like you would find at the bottom of a waterfall or in a boiling pot.

For these four words, they either share large parts of their definitions or refer to each other.

Where they are different is in their usual contexts and/or phrases:

• foam is if anything the most general and the hypernym of the set. It can refer to a liquid

  sea foam

  for the foam that is created at the crests of waves or

  foaming at the mouth

  a foam made of saliva, or a solidified form like a

  foam cushion

• froth is more likely to be related to food like a

  frothy meringue

• lather is mostly related to use of soap, thicker than suds.

  Lather. Rinse. Repeat

  are the instructions for when one creates a lather with shampoo in one's hair. But also, horse sweat as in:

  beat a horse into a lather

• suds are lighter (larger bubbles) than a lather, and often associated with soap for cleaning both personal and laundry.

  soap suds

Froth is typically reserved for beverages, though there are times when it is used to describe bubbles from saliva. Generally speaking though, it is the most limited word on the list in terms of common usage, and it is most often associated with beverages (or used in metaphors, in lieu of the "icing on the cake").

Foam, on the other hand, is probably the most commonly used word on the list, as its meaning has grown to cover all sorts of ideas: polystyrene (Styrofoam), froth, etc. Andrew stated in the comments that "shaving foam" is the correct term in the UK, but I believe in the US there's a tendency to avoid "foam" for all soap and cream related purposes - we would simply refer to it as "shaving cream". However, foam is the most general term, so no matter what, it can apply (in the US) to almost any bubbly substance. You can't go wrong with foam!

"Lather" is not only a noun, but a verb. According to the Cambridge Dictionary, it means "to produce lather from a soap, or to cover something in lather." As much as I hate to use circle definitions, I typically would describe "lather" as the product of "lathering". If you rub soap against your hands or skin, you are producing lather. It has a connotation of "cleaning", and it is almost always associated with "soap".

Suds is a more common term, but almost exactly the same as lather - however, while lather carries a meaning of "the product of rubbing soap against something", suds is just soapy bubbles, and it is always soap and water.

tl;dr: use foam.