9th ed still using 8th ed books until new books right?

[Brother Glacius]

Just to be clear, cuz I'm old and my memory isn't what it used to be....for 9th ed, you use the 8th ed book unless a new one has been released yes?

[Ish]

Yes, for codices and codex supplements. The Specialist Detachments from the campaign supplements (e.g., Vigilis Defiant) aren’t allowed in Matched Play and YMMV as to whether or not you can use them in Open Play.

[Patrick]

Yes. With certain exceptions. Dark Angels and Black Templars each have an index that (I think) replaces both their Codexes ("Codices"?) and their Psychic Awakening rules. Other factions have updated errata that include new weapons stats (flamer ranges, etc.,) and updates to reflect new rules (e.g., weapons that can target characters now say they ignore "Look Out Sir!"). They're on the Warhammer Community FAQs page.

[Ish]

Codices is the proper plural, following the standard rules for words ending in an “–ix” or “–ex,” for example appendix becomes appendices, index becomes indices, and so forth. Codexes is considered acceptable by most dictionaries, but generally discouraged by most editors... except at GW who uses it by default. 

Thank you for coming to my TEDTalk.

[jesselowe]

21 minutes ago, Ish said:

Codices is the proper plural, following the standard rules for words ending in an “–ix” or “–ex,” for example appendix becomes appendices, index becomes indices, and so forth. Codexes is considered acceptable by most dictionaries, but generally discouraged by most editors... except at GW who uses it by default. 

Thank you for coming to my TEDTalk.

That's why we have one sex but two sices. (Or more, for some species, I suppose)

[Ish]

That’s actually a very interesting case, as sex does derive from Latin roots, along with most “–ex” ending words, but it’s treated as a regular plural instead of an irregular plural. Probably due to being a much more commonly used word and undergoing stronger Anglicisation. 

But, this is really off topic...

[Brother Glacius]

How many tyrannosaurus rices does it takes to have a battle of the sices?