- 1. In adding this suffix to a verb, the general rule is to drop a silent e (livable, lovable) except after a soft g (manageable) or sibilant c (peaceable). When a verb ends with a consonant and a y (justify, indemnify) change the y to i before adding -able (justifiable, indemnifiable). Verbs ending in -ate drop that syllable before adding -able (appreciable, demonstrable).2. -able , -ibleThere are no reliable rules for knowing when a word ends in -able and when in -ible; see Appendix for a list of some of the more frequently confused spellings.
Bryson’s dictionary for writers and editors. 2013.