Lord Revan wrote:so these are for story idea I got.
1. if they of equal rank?
"Brother" or "Chaptername" or "Son of Primarchname"
2. if the marine being adressed was of lower rank then the the other marine?
Same as above, with emphasis on the latter two.
3. if the marine being adressed was of higher rank then the other marine?
Any of the above, plus "Brother-Rank" or "title" or "Lord", depending on the degree of rank difference and the degree to which the chapters respect one another. For instance, a battle brother of the Dark Angels is unlikely to address a Space Wolf as anything but "Space Wolf" or "Sergeant/Captain" unless he's talking to the chapter master. On the other hand, a White Consul might address an Ultramarine exactly as another Ultramarine might.
second same questions but the chapter the marine being adressed is from is the Grey Knights?
"Why, noble Astartes, I do not recognize the device on thy pauldro-
hurk! Gasp. Iihhhh..."
or
GK: "Greetings, brother sergeant. Your squad is sequestered by the Ordo Malleus to aid us in the destruction of the foul Chaos menace!"
SM: "Fuck you, shinybitch."
BAM!
GK:
Hurk! Gasp. Iihhhh...
third same basic questions but instead of another marine the person being addressed is a Adepta Soritas trooper/officer?
"Sister" / "Rank" / "TypeofSister" / "Daughter of the Emperor".
fourth again same basic questions but the person being adressed is an imperial guardsman (or an IG officer)?
Anything he wants. The Astartes is the grandson-by-adoption and grandson-by-blood of
God Himself. Guardsmen, even the highest ranking, are mere mortals. I'm fond of the completely unofficial "child(ren) or Terra", but address-by-rank would be common, I suspect.