ful carefully 小心謹慎地 [Card #26; 字卡第26張: 第2個單字]

ful: a suffix meaning "full of"【動詞或名詞，字尾加 ful 變成形容詞】
Some more examples（更多例字）：tactful, handful, thankful, flavorful, grateful, ungrateful, graceful, disgraceful, tasteful, distasteful, wasteful, playful, painful, faithful, careful, armful, harmful, watchful, awful, lawful, healthful, helpful, plentiful, restful, respectful, disrespectful, successful, unsuccessful, stressful, deceitful, peaceful, meaningful, fearful, cheerful, willful, skillful, blissful, pitiful, rightful, frightful, delightful, insightful, colorful, wonderful, hopeful, forceful, forgetful, thoughtful, resourceful, joyful, powerful, mouthful, doubtful, youthful, roomful, spoonful, cupful, trustful, truthful, fruitful, useful, beautiful, merciful, purposeful