階 - Higher RANKS Take Higher Ground, All the Rest Stay on the Ground FLOOR

Readings & Meanings:

かい

floor (of a building), rank

Common Usage:

階級

階段

三階

Examples:

江戸時代は士農工商という階級制度が定着した時代だった。

階段から落ちて怪我をした。

三階のアパートの住民はいつも夫婦喧嘩をしている。

Translations:

The Edo Period was the period when the social hierarchy of samurai, farmers, artisans, and merchants was established.

I fell down the stairs and hurt myself.

The couple who reside in the third-floor apartment are always having domestic squabbles.

Radical:

阝 on the left, so the radical is Kozato, an abbreviated form of 阜, a picture of a pile of earth.

阝, Kozato, is different from 阝 (Oozato), as explained in my post on 降.

The phonetic element is 皆. We should already know 皆 as meaning "everyone."

比 is on the top of 皆, and we should know it from 比べる, to compare. 比 is a pictograph of two people lined up.

The bottom part of 皆 is a squished version of 自, self. It acts as an action indicator.

Let's just think of 皆 in 階 as "line up" and 阜 as "higher earth." Thus "rank," as in when you line up people you will place the higher-ranked people higher than the rest. You can also think of "stairs," if you think of a long line of people, one after the other, marching up the stairs. If you've ever been in a busy train station in Japan, you can easily imagine this.

References:

http://www.kanjinetworks.com/indices/radindex.html
http://www.thejapanesepage.com/node/kanji/ka.htm