Have you ever wondered why your grandmother writes heroes and you write heros? Or you write dominoes and then you see dominos published somewhere and start to doubt your spelling prowess? Trust me, it’s not you! It’s the woes of the final single <o>.
There are many multisyllable words that end with a final single <o> and a lot of confusion around adding suffix -s or suffix -es to pluralize or modify the verb tense of these words.
But the list is pretty short when it comes to single-syllable words ending with a final single <o>, so let’s start there.
do, go, lo, mo, no, so, to, yo
All single-syllable words that end in a final single <o> are native English words and always take suffix -es, both with plural suffix -es and verbal suffix -es. But . . . this list is very short.
We generally only see the verbal suffix -es with <does> and <goes>. According to Neil Ramsden’s Word Searcher, the other single-syllable words ending in a final single <o> include: lo, mo, no, so, to, yo. Of these, the only one that I think we would possibly see pluralized is <noes> as in, "How many noes do I have to take before I get a yes?" Having said that, the rule does apply to all single-syllable words that end in a final single <o>, even though we typically only use <does> and <goes>.
The rules/patterns are much more nuanced for multisyllable words that end in a final single <o>. We'll summarize the details for all the curious educators and perhaps the really inquisitive and/or older student. For those using our Pinwheels early literacy curriculum, this is beyond the scope of what is taught in the Pinwheels Year 2 go/do lesson.
Multisyllable words that have a final single <o> were originally all loan words, meaning they came to English through other languages. No native English multisyllable words have a final single <o>. But some of these loan words have become so established as part of the English speaking experience, as if they were native, that they take suffix -es, just like all truly native English words that end in <o> . . . which are all single-syllable words.
Examples that fall in this category include: potatoes, tomatoes, volcanoes, echoes, dominoes, mosquitoes . . . There are others, and investigation and inquiry can lead you to identify those that follow this pattern. It would be interesting to do a word sort and then look at the etymology of the words where suffix -es has been added to see if you concur that those words have essentially become native English words. After saying all this, we then have to consider that things get more complex because some publishers have started to use suffix -s in place of suffix -es for a few of these words, like volcanos.
In the following cases of multisyllable words ending in a final single <o>, it is certain that a suffix -s is used:
- where the final <o> has another vowel letter before it (radios, videos)
- where the singular is an abbreviation (hippos, memos)
- where the word is a proper name
- where the word is an Italian musical term (pianos, sopranos, adagios)
Most other multisyllable words ending in a final single <o> also take suffix -s, with the exception of those words that we’ve come to consider as native English words described above.
(Source: Real Spelling Online Toolbox)
