Per 
The 5 main object classes,Safe,Euclid,Keter,Thaimiel,Apollyon,in short SEKTA.
The Box Metaphor Safe:if you can lock it up and put it in a box and leave it alone and nothing happens its safe.Euclid if you can lock it up and put it in a box and leave it alone and not knowing what will happen its Euclid.Keter if you can lock it up and put it in a box and leave it alone and all hell breaks loose its Keter.Thaumiel if you can make a box out of it to contain Keters its Thaumiel.And finally Apollyon there is no box that can contain it and you should run for your life.
Class Safe:An Scp thats properties can be controlled, are understood and pose no immediate threat,
Class Euclid:Named after the Greek Mathmatician,Euclid of Alexandria. An Scp that is difficult to contain,moderately dangerous and isn't well understood.
Class Keter:Hebrew for Crown,And Scp that is extremely hard to contain and is very dangerous.
Class Thaimiel:Kabbalah for the Tree of Life.An Scp that has properties useful for the foundation.
Class Apollyon:A translation of the name Abaddon,in Hebrew 'The Angel of Death'.An Scp near impossible to contain,it's properties pose a serious and immediate risk to all human life.
Class Explained:Sn Scp that's properties are explainable and are common place among humanity to the point no one takes notice.
Class Neutralized:An Scp that has been Successfully neutralized.
Class Maksur:Araibic for 'broken'.An Scp that is broken or damaged but not neutralized,if all the pieces were to be brought back together the Scp would be revived. Such as the Broken God. (an Scp-001 proposal)
Class Zeno:Medium containment difficulty,low threat.Refers to Scp-2005.
Class Embla:Refers to Dr.Mann's Scp-001 proposal.In The Pagen Creation Myth the first two humans were created by three gods by two trees Ash and Elm.From the trees the first man and woman were created:Ask And Embla
Class Euclid-Ignotus not quite sure what this one means but it relates to Scp-655 and Scp-2003
Class 53:Highly intrusive, unknown capabilities,unknown nature.Refers to Scantron's Scp-001 proposal.
Class Humanoid:Refers to the entites in Djoric-Dmatix's proposal for Scp-001.
Class Keter-Thaumiel:Refers to Djkaktus's proposal for Scp-001
Class Yesod:Spikebrennan's proposal for Scp-001,refers to an empty space beneath the 05 council's headquarters.
Class Non-Anomalous:WJS proposal for Scp-001.A document about concensus reality.
Class Safe-Prodest:Refers to Scp-066.
Class Euclid-Imetus:Also refers to Scp-066,Imetus comes from the latin word meaning to 'attack'.
Class Safe-Impetus:Refers to Scp-984.
Class Euclid-Nunctii:Comes from the latin word 'news'.Not sure what this object class refers to though.
Class Nehemoth:Refers to the 'Enemy' in Scp-2998.
Class BFF:Refers to Scp-2790,needs to be pet often.
Class Former:Refers to Scp-2602,an old library that people are compelled to make others aware that it is an old library.
Class Glorious:Refers to the royal crown in Scp-1561.
Class Kronecker:Refers to Scp-2062, appears on random Scp object computerized entries and change item's class,descripion and special containment procedures to make that entity exempt from containment.
Class Decomissioned:An in-universe way of deleting bad Scps.
Class Olympia:Scps that are no less than 100m in height.
Class Gevurah:Refers to the 4th iteration of Scp-3666,An Scp that has the ability to influence the inner structure of the foundation.
Class Heimal:Two of more phenomena or entites that mutually contain each other's properties.
Class Dammerung:Refers to the cognitohazard that is Scp-2718.
Class Euclid-Numen:Refers to Scp-1564,numen means spirit or divine power over an object or place.
Class Safe-Reliquia:Refers to Scp-1962.
Class Scalf:Refers to Scp-586.
Class Undefined:Refers to Scp-3942
Class N/A:Refers to Scp-3930,which does not exist(05 Restricted)
Class Oblique:Refers to Scp-2786,there is nothing that can be done and it's already to late!
Class None:Also refers to Scp-2786,conflicting report that states Scp-2786 does not exist and so therefore containment is unnecessary.
Class Declassified:Refers to the musical albums released to the population to help them adjust the imminent event XK-610-Omega.
Class Kusum: Containment Abandoned!
Class Euclid-Flecto:Refers to Scp-625,in latin etymology flecto means uncertain origin.
Class Keter-Alterius:Refers to Scp-1141,a restaurant that appears in the same zoo everyday 30 minutes prior to opening.
Class Null:Refers to Scp-000,No information to give.
Class Mild:An object that is almost completely safe to interact with,unless handled in extremely irresponsible manner.
Class Keter-Provisi:Refers to Scp-2721.
Class KE@#%^SUPE1337KETER!!!!!!1!!!1!111!!#$%^:Refers to Scp-732,The Scp's records have been altered by Scp-732 itself.
Class Netzach:Refers to Billith's proposal for Scp-001.
Class In Doubt:Refers to the philosophy book about humanity in Scp-2685.
Class Tiamat:Refers to the hyperphysical entity in Scp-3895.
