Know difference between Lesbian and Yuri?

Recently I’ve been posting list of newly starting Anime from July in Japan.

New Anime Starting July in Japan Part One
New Anime Starting July in Japan Part Two
New Anime Starting July in Japan Part Three

And realized that recent Anime has a tendency of Yuri.
I’ve been using Lesbian(in Japanese Lezu) and Yuri alternatively without knowing the difference.

There aren’t firm definitions for both words as genre.
You know, genres are vague.

CAUTION: Lezu in this post refers to genre of Anime, not real people.

Here are several post and sleds discussing the difference of Lezu and Yuri.
-Yuri is happier
-Yuri is more pure
-Yuri is only kissing and hugging, Lezu goes further.
-Lezu is grotesque, Yuri is fantasy
-Lezu and Yuri is completely different
-In Yuri, girls don’t see female as sex appeal, in Lezu they do.
-Yuri is Girls love

Seem like there is a big difference between Lezu and yuri anime and Manga.
I still can’t define it clearly but here is my conclusion.

Yuri Anime is about girls and girls in relationship between best friend and a lover.
Lezu Anime is about girls and girls in relationship of lovers or sex friends.

Here is a post of Uncyclopedia about yuri.
The impression I get is this is a definition of Lezu genre. Can you sense the difference?

List of beautiful Yuri Anime
-Maria-sama ga miteru
-StrawberryPanic
-Hito Hira
-Kanamemo
-Aoii Hana
-Sasamekikoto
-Kareido Star
-Kanazuki no Miko
-Yami to Boushi to Hon no Tabibito
-MADLAX
-PIECE@PIECES
-Blue_Drop
-Rei-Akai Chou
-Rule of rose
-Candy boy
-Mnemosyne
Recourse