directionality

The directionality of a script says, how it is written. There is:

ltr

left to right - text begins at the top left edge of a writing area and is written in lines extending right. When there is not enough space left on such a line, a line break is made at a select place determined by grammar and typographic rules, and writing is resumed at the left of the line below.

rtl

right to left - text begins at the top right edge of a writing area and is written in lines extending left. When there is not enough space left on such a line, a line break is made at a select point determined by grammar and typographic rules, then writing is resumed at the right end of the line below.

var

variable - some script can be used either left to right or right to left. This can be entirely up to a writers preference, or be different for socio-cultural groups, or have been varying at different times in history.

und

undetermined - for some historic scripts.

none

for unwritten scripts and signalled communication.