| Object | HTk.Kernel.Core |
| ObjectID | |
| 1 (Data Constructor) | HTk.Kernel.Core |
| 2 (Type/Class) | HTk.Kernel.Core |
| objectID | HTk.Kernel.Core |
| ObjectKind | HTk.Kernel.GUIObjectKind, HTk.Kernel.Core |
| objectkind | HTk.Kernel.GUIObject, HTk.Kernel.Core |
| ObjectName | |
| 1 (Type/Class) | HTk.Kernel.GUIObjectName, HTk.Kernel.Core |
| 2 (Data Constructor) | HTk.Kernel.GUIObjectName, HTk.Kernel.Core |
| objectname | HTk.Kernel.GUIObject, HTk.Kernel.Core |
| obj_type | HTk.Toolkit.TreeList |
| obj_val | HTk.Toolkit.TreeList |
| Oblique | HTk.Kernel.Font, HTk.Toplevel.HTk |
| Off | HTk.Kernel.Resources, HTk.Toplevel.HTk |
| offset | |
| 1 (Function) | HTk.Textitems.TextTag, HTk.Toplevel.HTk |
| 2 (Function) | HTk.Toolkit.MarkupText |
| oID | HTk.Kernel.Wish, HTk.Kernel.Core |
| OKType | HTk.Kernel.Wish, HTk.Kernel.Core |
| omega | HTk.Toolkit.MarkupText |
| omikron | HTk.Toolkit.MarkupText |
| On | HTk.Kernel.Resources, HTk.Toplevel.HTk |
| oomega | HTk.Toolkit.MarkupText |
| oomikron | HTk.Toolkit.MarkupText |
| open | HTk.Toolkit.TreeList |
| openedFolder | HTk.Toolkit.GenGUI |
| oplus | HTk.Toolkit.MarkupText |
| OPTIONMENU | HTk.Kernel.GUIObjectKind, HTk.Kernel.Core |
| OptionMenu | HTk.Widgets.OptionMenu, HTk.Toplevel.HTk |
| or | HTk.Toolkit.MarkupText |
| orient | HTk.Kernel.Configuration, HTk.Toplevel.HTk |
| Orientation | HTk.Kernel.Resources, HTk.Toplevel.HTk |
| OST | |
| 1 (Type/Class) | HTk.Kernel.GUIObject, HTk.Kernel.Core |
| 2 (Data Constructor) | HTk.Kernel.GUIObject, HTk.Kernel.Core |
| Other | HTk.Kernel.Font, HTk.Toplevel.HTk |
| otimes | HTk.Toolkit.MarkupText |
| outline | HTk.Canvasitems.CanvasItem, HTk.Toplevel.HTk |
| outlinewidth | HTk.Canvasitems.CanvasItem, HTk.Toplevel.HTk |
| OVAL | HTk.Kernel.GUIObjectKind, HTk.Kernel.Core |
| Oval | HTk.Canvasitems.Oval, HTk.Toplevel.HTk |
| overlapping | HTk.Canvasitems.CanvasTag, HTk.Toplevel.HTk |
| overstrike | HTk.Textitems.TextTag, HTk.Toplevel.HTk |