On seeing the word <*symettry>, I knew it was wrong, but it's no use just knowing a spelling is wrong and knowing what the correct spelling is - you need to know why! And I was itching to know why!
I summoned up my courage and asked the teacher if I could use her computer to look something up. I then went to www.etymonline.com and found this:
So, it seems that <symmetry> means "having a common measure" and is built like this:
sym (meaning "together")
metre (meaning "measure" - using British spelling)
-y
So that's sym + metre + y --> symmetry
The single silent <e> at the end of <metre> is replaced by the vowel suffix <-y>, just like the single silent <e> in <write> is replaced by the first letter of the vowel suffix <-ing>, so that:
<write> + <ing> --> <writing>.
This is said out loud as W-R-I-T-E plus I-N-G is rewritten as W-R-I-T-(no E)- I-N-G
Not only is this a great spelling lesson (it teaches what to do with that final non-syllabic or 'single silent' <e> when we add a vowel suffix), but it's also a great vocabulary lesson - and a great maths lesson! How better to explain what 'symmetry' means than to help the kids understand that it's about the "together" "measure" - "having a common measure" - objects/lines/points a 'same measure' from the mid-line/mirror line. So 5cm away on one side of the line of symmetry must be 5 cm away on the other side too.
This investigation took about 5 minutes from start to finish - I could have delved deeper into related words and looked at the prefix <syn->, because that is a variant of <sym->, it's just that you can't really pronounce something like <*synmetry> very easily. (Try to say it out loud quickly a few times). So before an <m>, we use <sym-> instead.
That could lead to a study of other prefixes that have variant forms depending on what they are being fixed to. Maybe you'd like to look into that yourself?
Oh, wait! You don't have to - I couldn't resist. Below is what www.etymonline has to say. Note how I used a hyphen after the <sym> to show the search engine it was a prefix.
I then used http://www.neilramsden.co.uk/spelling/searcher/index.html to see which words had <sym> or <syn> in them. Here are some examples:
symphony - "together" "sound"
symbiosis - "together" "life"
sympathy - "together" "feeling" (<pathos> = "feeling")
synonym - "same" "name"
synthesis - "together" "put"
synchronise - "together" "time"
And so, one very tiny but very big fat juicy mistake can lead to a lot of learning. And that's why we need to celebrate when we (or our students) make a mistake. Because if you we the interest to find out why a word is spelled the way it is (and not just correct the mistake), then we really can learn from our mistakes! And that changes embarrassment about mistakes into excitement! So mistakes are awesome! bring them on!