Thread:Hibridragon/@comment-11293505-20160215143838/@comment-18812574-20160226193944

They have lightbulbs in the Soul Society. I mean the Research and Development Dept. has computers, so some of the lights we see in the Seireitei anyway might run on electric Reishi or something.

And they have TV soap operas like "My Roommate was a Hollow" and so-forth. (jk, jk)

But as to how Reiryoku works that analogy isn't maybe a very accurate one. Reishi is the energy and/or that makes up the spiritual realm. Kind of like molecules and atoms only in a Sixth-Sense dimension. Reiatsu is an expression of the power of a "spiritual" being (Shinigami, Quincy, Fullbringers, Hollows, etc). Even non-spiritually humans might have a very small amount of Reiatsu if they are able to emit their Reiryoku, sort of like infrared or those tiny electrical signals that run throughg the human body, possibly. Reiraku are threads of spiritual energy that, when percieved, allow you to track a specific person's Reiatsu. Reikaku is the act of sensing spiritual pressure (Reiatsu.)

That all defined, Reiryoku is possibly the most complex out of the four "Rei's" in Bleach. It is something I believe has so-far been limited to Shinigami and Hollows when explained, although it is stated that ALL spiritual beings and humans have Reiryoku. Reiryoku is defined sort of as the base spiritual power that a being actually has. It is your "resevoir" of spiritual power in other words. Humans with high Reiryoku can usually see Hollows and Ghosts, Shinigami with high Reiryoku may some day be able of achieving Bankai. Ichigo has possibly one of the strongest Reiryoku in the series (besides say Yhwach, Aizen, Kenpachi, Yamamoto, the "giants" of spiritual pressure and so-forth) because (I believe this was stated somewhere) his is one that can constantly expand: he has no limit and that's his greatest strength, he's constantly growing.

So your Reiryoku can change over time, either growing or (say in a case where someone loses their power) shrinking. Reiryoku is generated in your spiritual core, which varies between races. For example, the source of a Shinigami's power is their hakusui (soul sleep) whereas a Fullbringer's "core" is the remnant Hollow Reiryoku imbued in their souls before birth. Since not all of these "cores" have been defined canonically there is some freedom of interpretation here, of course. Also it appears that the strength of a person's Reiryoku can depend on a variety of factors, such as their willpower Aand determination. (ie, Ichigo vs. Renji "I will save my friend!")

Reiatsu = Spiritual pressure (Reiryoku expressed physically) Reiryoku = The actual spiritual power a being has