pensive

a. 沉思的, 哀思的, 忧郁的

副词:pensively 名词:pen-siveness 

pen.sive

adj.（形容词）
Deeply, often wistfully or dreamily thoughtful.
沉思的，冥想的：通常是忧郁或朦胧地深深思考的
Suggestive or expressive of melancholy thoughtfulness.
忧心忡忡的，郁郁寡欢的：让人联想起或表达忧郁的沉思的

来源：
Middle English pensif
中古英语 pensif
from Old French
源自 古法语
from penser [to think]
源自 penser [想]
from Latin pôns3re [frequentative of] pendere [to weigh] * see (s)pen-
源自 拉丁语 pôns3re [] pendere的重复动词 [权衡] *参见 (s)pen-

【引伸】
pen.sively
adv.（副词）
pen.siveness
n.（名词）
<参考词汇><同义词>pensive,contemplative,reflective,meditative,thoughtfulThese adjectives mean characterized by or disposed to thought, especially serious or deep thought.
这些形容词主要用于形容严肃或深沉的思想。
Pensive often connotes thought of a wistful, dreamy, or sad quality:
Pensive 意指一种愁闷、冥思或忧伤的思想：
例句：
.while pensive poets painful vigils keep. (Alexander Pope).
.当冥想的诗人守夜忧思时. （亚历山大·柏蒲）。

例句：
Seeing the depth of her despair, he grew pensive.
看到她陷入无限的绝望，他沉入深深的忧思中。

Contemplative implies slow, directed consideration,often with conscious intent of achieving better understanding or spiritual or aesthetic enrichment:
Contemplative 暗指一种缓慢而有指导的深思，常带有为了更好地理解或获得精神或美感上的富足的有意识的意图：
例句：
.The Contemplative Atheist is rare . . . And yet they seem to be more than they are. (Francis Bacon).
.喜欢深思的无神论者是很罕见的…他们看起来实际更喜欢思考. （弗朗西斯·培根）。

Reflective suggests careful, analytical deliberation, as in reappraising past experience:
Reflective 暗指一种如总结过去的经验教训等仔细周到和具分析性的思考：
例句：
.Cromwell was of the active, not the reflective temper. (John Morley).
.克伦威尔生性躁动，缺乏深思熟虑的性格. （约翰·莫利）。

Meditative implies earnest, sustained thought:
Meditative 暗指一种热切而持续的想法：
例句：
The scholar was reticent, aloof, and meditative.
这位学者寡言少语、离群索居而且总在沉思。

Thoughtful can refer to absorption in thought or to the habit of reflection and circumspection:
Thoughtful 可指陷入沉思或周密考虑及思考的习惯：
例句：
The judge looked thoughtful, then granted the motion.
法官沉思了一会儿，然后批准了这一议案。

例句：
Thoughtful voters viewed the proposed legislation with alarm.
深思熟虑的投票人谨慎地看待这一立案法律