1. 1 on class
2. 1 in definition
3. 1 in notes

On grammatical class:

na'u

convert selbri to mex operator; used to create less-used operators using fu'ivla, lujvo, etc.

In definition:

cmavrna'u

x₁ is the selma'o "NAhU".

In notes:

mekseia

x₁ is a part of Lojban text representing rule 'mex-operator' according to the first edition of the book 'The Complete Lojban Language'.