adjective endings

[kawaii_san]

could someone explain me the difference between, for example: yasashii, yasashisa, yasashiku
or
fukai, fukasa, fukami, fukaku

I mean, the -ii/i,-sa,-ku,-mi endings...

oh and I recently even heard the word "itoshiki(愛しき)" but I'm not sure if that's an adjective. so if that's an adjective, what does the -ki ending mean?

[Yudan Taiteki]

I'll let someone else direct you to a place for your main question, but the -ki ending in itoshiki is an archaic ending that goes on adjectives when they are modifying nouns. It's sometimes found in modern Japanese if the writer wants to give an archaic or formal stylistic touch to what they are writing.

[richvh]

やさしい and ふかい are the dictionary forms of adjective. やさしさ, ふかさ and ふかみ are nouns derived from those adjectives. The さ ending indicates a quality (gentleness, depth) and the み ending an instance, if I remember right. ふかく and やさしく are adverbial forms; they would modify the following verb or adjective. As for 愛しき, it's an archaic pre-noun form of the adjective 愛しい (in classical Japanese, pre-noun and sentence-final forms of verbs and adjectives were different.)

[kawaii_san]

Oh I think I got it For example:
Fukai - This is a deep hole
Fukasa/fukami - Let's check the depth of this hole
Fukaku - We'll deeply pierce it.

Dumb examples -_-

Are the -sa and -mi endings exactly the same?

[inuinu]

Are the -sa and -mi endings exactly the same?

深み＝深い場所
「彼は心に深みがある立派な人物だ」「あの穴の深みは蛇がいて危険だ」
（これらの場合に限ってのニュアンスの話なので、「〜み」＝「場所」ではないです。
「厚み」の場合は「厚さ」とほぼ同義として使われていて、
「厚い場所」というニュアンスは薄いです。

深さ＝深度・深さの度合い
「彼の心の深さは尊敬に値する」「あの穴の深さを調べてみよう」


↓の中段あたりの「◆ことばの話847」に、「み」に関するちょっとしたお話があります。
http://www.ytv.co.jp/announce/kotoba/back/0801-0900/0846.html

日本人にとっても、「〜み」はなかなか「深み」のある議題のようです。