Word Families
A word family consists of a base word and all its inflected and derived forms. The concept, central to Paul Nation's vocabulary research framework, assumes that knowing one member of a family provides partial access to others through shared form and meaning.
Example
The word family for educate:
educate, educates, educated, educating, education, educational, educationally, educator, educators, re-educate, uneducated
All forms share a recognisable base and related meaning, connected through morphological processes (inflection and derivation).
Nation's Levels of Word Family
Nation (2016) describes word families at different levels of inclusiveness:
| Level | Includes | Example additions to help |
|---|---|---|
| 1 | Base word only | help |
| 2 | Base + inflections | helps, helped, helping |
| 3 | Level 2 + frequent, regular derivations | helper, helpful, helpless |
| 4 | Level 3 + less frequent derivations | helpfully, helpfulness, helplessly |
| 5 | Level 4 + infrequent, classical derivations | unhelpful |
| 6 | Level 5 + further derivations | unhelpfully, helplessness |
Most vocabulary research and the Academic Word List use Level 6 families, which is the most inclusive definition.
Counting Vocabulary Size
Word families are the standard unit for measuring vocabulary size:
- A native adult English speaker knows approximately 20,000 word families (Nation & Waring, 1997)
- The most frequent 2,000 families cover ~80% of general English text
- 3,000 families + the AWL cover ~90% of academic text
- 8,000–9,000 families are needed for unassisted comprehension of general text (Nation, 2006)
The Assumption of Transparency
The word family concept assumes that morphological relationships are transparent — that knowing educate helps you understand education. This is broadly true for regular, productive affixes but breaks down with:
- Opaque derivations: department ← depart? The semantic connection is weak
- L2 learners: research (e.g., Ward & Chuenjundaeng, 2009) shows that learners do not automatically recognise family members, especially at lower proficiency levels
- Polysemous bases: interest → interesting, interested, disinterested, uninteresting — the family is transparent, but interest itself has multiple meanings (see Polysemy)
Teaching Implications
- Teach Word Formation explicitly — affixes, compounding, conversion — to help learners exploit family relationships
- Do not assume that teaching one family member automatically transfers to others; recycling across members is necessary
- Use Vocabulary Learning Strategies that leverage morphological analysis (word parts strategy)
- Word family knowledge supports reading comprehension by enabling learners to handle derived forms they have not explicitly studied