N/A or sometimes n/a is a common abbreviation in tables and lists for the phrase not applicable, not available, not assessed, or no answer.

Whats does na mean?

NA is a written abbreviation for not applicable or not available.

Why is it called na?

The name derives from the English soda and Latin sodanum for "headache remedy". The symbol Na derives from the Latin natrium for "natron" (soda in English). ... Long recognized in compounds, sodium was first isolated by Davy in 1807 by electrolysis of caustic soda.