Colon classification

Empty, emptying etc

Empty digit

An empty digit (Z, 0, 9) is effectively not there. The leading 9s in the octave device (7, 8, 91, 92 etc) are empty digits. It is as if 91 and 92 are new single digits that follow 8.

Emptying digit

An emptying digit (T, V, X) nullifies the semantic value of the preceding digit, but not its ordinal value. So in the sequence K, KX, L the X causes KX to sort after K, but not to be a subcategory of K. KX here is co-ordinate with K and L just as M is - it's as if KX is a new single digit that comes between K and L. NB that when these digits are initial digits, they don't have any emptying effect (because there is no preceding digit!)

Empty-emptying digit

An empty-emptying digit (U, W, Y) combines both roles. It enables infinite interpolation between any two digits, eg

L Medicine
LX Pharmacognosy
LY1 Nursing
LY7 Anaesthiology
M Useful arts

Without empty-emptying digits, we would only be able to interpolate 3 times between L and M (LT, LV, LX).

If there was an LX1 in the above list, it would be a subcategory of LX. LY1 and LY7 however are not subcategories of LY, because a number LY cannot exist, just like a number 9 cannot exist with the octave device. Again, it's as if LY1 and LY7 are new single digits that come between LX and M.

(I think of empty-emptying digits as having 'zero width' or being 'control characters' - they aren't actually in the final output, they just indicate how the other characters are to be interpreted).

Partial comprehension

Better thought of as agglomeration - I think 'partial' here is meant to be read as 'of parts', ie 'comprehension of parts'.

Is done with Z as a contextual emptying digit (normally it's just an empty digit) and * as an anteriorising digit (to make Z sort before 'no digit').

16 Upper extremity
17*Z Head and neck
17 Neck
18 Head