Glossary · Word parts and vocabulary
What is a word sum?
Definition
A word sum writes a word as its parts joined by plus signs, such as re + play + ing = replaying, showing how the parts build the word and its spelling.
Word sums make morphology visible. The student writes each part, joins them, and checks the result. When spelling changes at a join, the sum shows exactly where: hope + ing = hoping, with the e dropped.
They work in both directions. Building a word from parts teaches spelling. Breaking a word into a sum teaches reading and meaning. Either way, the student has to look at every part.
Word sums also help students notice when a suffix rule applies. Run + ing = running shows the doubled n; happy + ness = happiness shows y changing to i. Writing the sum first, then the word, gives a student a clear moment to apply the rule.
In a lesson
The student writes un + help + ful = unhelpful. Then they try a harder one: care + less + ly = carelessly. They check that no letters were lost or changed at the joins.
Examples
Each word with its spelling units, one per sound.
- unhelpfulu·n·h·e·l·p·f·u·l
- carelesslyc·are·l·e·ss·l·y
- hopingh·o·p·i·ng
Words come from our lexicon, checked against a pronouncing dictionary. Words a student sees in our assessments are left out.
Why does this matter for the record?
A page of word sums is good evidence of suffix-rule knowledge. Note errors at the joins; that's where the rules live.
Rate each skill as you teach it
Needs support, Developing, Secure. The rating schedules the review and builds the report.