下层的英文及参考例句

下层的英文：

substratum

参考例句：

Disadvantaged families

下层贫困家庭

evergreen undershrub

常绿下层灌木

Party activists with lower middle class pedigrees are numerous.

党内积极分子中中产阶级下层出身的.很多。

The salt water, being more dense, flows upstream under the fresh water which is flowing downstream

淡水在上层向下流动，比重更大的盐水在下层逆流向上。

At the nadir of...

在…的最下层[最低处]

He belongs to the lower middle class.

他来自中产阶级下层。

The lower deck is more convenient.

下层甲板更方便些。

Tramps are in a low stratum of society.

流浪汉生活在社会的下层。

Tramps are from the lowest stratum of society

流浪汉来自社会最下层。

aristocrats who regarded the rabble with deep contempt.

对下层民众极其蔑视的贵族们

substratum是什么意思：

n. 下层;地基;根基

"For soft substratum, dig out the top layer (5 - 10 cm thick), sort out the animals, identify and count them."

若是软基质,用小铲挖出表面5-10厘米厚的基质,找出砂泥中的动物,点算和鉴定。