Forming singular to plural nouns

I am boldly assuming that you have no problem with the basic rules of changing singular nouns to its plural forms as I write this.  You know the drills - adding 's' behind most words, changing 'y' to 'ies', adding 'es' to words ending with 'o', etc.

Did a little search on youtube today and found a video that is an idea for lower primary English teachers, to add some interest to your lessons when you are at this topic.  All of us should have no problems clearing the words in the video.  Go ahead, try it:

video for teaching lower primary:

What I have here is a little extra information.  We know that there are always some nouns that are always singular?  Can you think of a few?  Example: Gold

They are silver, wheat, corn, cotton, sugar, copper, etc.

What about words that may mean singular or plural?  This is easier, right?  Example: Sheep

They are cod, deer, salmon, bison, moose, fish, etc.

Fish?  I know this will create some contention.  Now, I learnt it as one fish, two fish, three fish...  It is only when there are more than one type (i.e. two types of fishes) that we use the word 'fishes'.  Then again, as I went through NIE's teacher training, the lecturers say that the boundaries have been blurred along the way and teachers started to accept fishes for as long as there is more than one fish, so I guess it is alright.

The final two points I'll bring up today deals with the unconventional types of plural forms.  No, I'm not going to touch on the 'foot' to 'feet' type.  I am highlighting this one about not adding the letter 's' at the end of the last word to form plurals.  Examples are passers-by, brothers-in-law, parents-in-law, etc.

The last one is on words that end with 'o', but not taking the 'es' form.  We simply put a letter 's' at the end of the word, just like the conventional ones.  They include:

piano, albino, zoo, sirocco, lasso, kangaroo, halo, momento, vidoe, portfolio, folio, cameo, studio, etc.

These final two examples take the last form of adding an 's' to it, but I have to remind students that these are words in short forms and should only be used within quotes (for example dialogues).  Know what I am referring to?  Well, they are much used by adults and children alike: memo and photo.  =)