What rule applies most closely to this word? avail Group I. If the root is a full word, the ending is usually -able. Group II. When the root is a full word except for a final e, the forms usually are spelled with -able. Group III. The suffix -able always follows i. Group IV. When the root has other forms built on the letter a, the -able form is used. Group V. When the root ends in hard c or hard g, -able is used. Group VI. When the root is not a full word,-ible is used. Group VII. When the word has an immediate -tion form, -ible is used. Group VIII. When the root ends in ns, miss, or soft c or g, ible is used.