To perceive with the eyes or intellect; detect.
看出，察觉出用眼看见，或用智慧察觉：查出
We substituted red balls for blue, to see if the baby would notice.
我们把篮球换成红球，看看婴儿能否觉察出来。
To catch sight of(something difficult to discern).
看见，察觉，辨别看到（很难察觉的）东西
recognize or detect by or as if by smelling.
使用嗅觉认出或者察觉。
Victor was ill-at-ease, and I could tell that Tess sensed something was wrong.
维克托显得局促不安。我看得出，苔丝也觉察出了有点不对劲。
be unconscious of any change
未察觉出任何变化.
During the trial, no one, not even Bassanio, noticed that the wise young judge was really Portia.
在审判期间，没有人能察觉出这位英明的年轻法官就是波西亚，连巴塞尼奥也看不出来。
Can you detect an escape of gas in this corner of the room?
你能察觉出这个屋角有煤气漏出来吗?
A Study of the Visual Verb "Look" and "See"
视觉动词“看”、“见”使用情况历时、共时考察
maybe were not noticed at all, except by Jack Halliday, who always noticed everything;
也许大家根本就没有察觉，只有在什么事情里都能看出门道来的杰克-哈代是个例外。
We enjoy staring at them, entranced as they go about their business, unaware(we hope)of our presence.
我们还喜欢出神地凝视着它们忙碌不停而不觉察（但愿如此）我们在观看。
Chueh-hsin looked up, and was surprised to see Chuehhui. "You're out?" he asked.
“你出来了？” 觉新看见觉慧进来，抬起头看了他一眼，不觉吃惊地问道。
Her trained ears detected the weakness.
她那受过训练的耳朵察觉出弱点来。
Miss Ley smilled almost imperceptibly.
莱伊小姐几乎察觉不出地微微一笑。
He noted the disharmony between husband and wife.
他觉察出这对夫妇不太和睦.
a scent of danger, fear, trouble
察觉出有危险、 恐惧感、 麻烦事.
I slipped from the room unseen, ie unnoticed.
我悄悄地溜出房间, 无人察觉.
They crept out without their parents'knowledge.
他们悄悄溜了出去,没有被父母察觉。