Suffixes: -able and -ible

Source: DfE, English Appendix 1: Spelling (2013) — Years 5–6 statutory suffixes
Origin: Latin -abilis and -ibilis via Old French Purpose: Guide to the suffixes -able and -ible — rules for choosing the right form, KS2 word list with definitions, and morpheme-based practice.

What they mean

Both mean "capable of being" or "worthy of being."

comfort → comfortable (capable of providing comfort)
possible → possible (from poss- + -ible; capable of existing)

The decision rule

Use -able when:

• The base is a complete English word: comfortable, washable, enjoyable
• The base ends in -ce or -ge — keep the e: noticeable, manageable
• There is a related -ation form: imagine → imagination → imaginable

Use -ible when:

• The base is NOT a complete English word: poss- → possible, horr- → horrible
• The base ends in -ss: access → accessible
• There is a related -ion (not -ation) form: digest → digestion → digestible

Morpheme matrix

-able word families

adorable → adorably · comfortable → comfortably · noticeable → noticeably

-ible word families

possible → possibly · terrible → terribly · visible → visibly · sensible → sensibly

Common mistakes

Dictation sentences

1. It was possible but not comfortable — barely manageable in the conditions.
2. The noticeable improvement was considerable and admirable in equal measure.
3. She was responsible for making the event enjoyable and memorable.
4. The incredible view was visible for miles — an indescribable sight.
5. Sensible decisions are not always desirable, but they are almost always advisable.

Source: DfE English Appendix 1: Spelling (2013). Decision rules derived from statutory guidance.