n. 看不见, 失踪, 消失

appear/disappear/appearance/disappearance/seem
记忆：
1. pear 梨，梨形为上小下大，表示渐渐显露，加前缀a（注意要双写辅音字母p）, 强调“出现”， appear vi. 出现， 好象（有假象的含义）It appears that the Tom appears in the classroom earlier than others. 好象汤姆到教室比其他人都早。
2. 加否定前缀dis-, disappear vi. 消失 SARS hasn’t disappeared completely, so we can’t relax ourselves. 非典还没有完全消失，因而我们不能掉以轻心。
3. 加名词后缀ance: appearance n. 出现，出场，外貌 We can’t judge a person by his appearance. 我们以貌取人。 格言： Appearances are deceptive. 人不可貌相。
4. disappearance n. 消失，失踪 The sudden disappearance of the boy worried the family a great deal. 男孩的突然失踪使全家非常紧张。
5. see 看见，seem vi. 好象（有一定依据的推断） It seems that a rain is coming. 好象要下雨了。
另类阅读：
When the sun appears, the moon will disappear. It seems that the appearance of the sun causes the disappearance of the moon.