Correct spelling


Correct spelling, explanation: this form comes from French, meaning military banner (estandart). In English it was probably adapted by merging stand and hard together (first in the same meaning as French). Therefore it should be written with d: standard, not standart.

Definition of standard:
adjective, common, accepted as usual
Sorry for inconvenience, but this is our standard procedure.
noun, something basic; rules of a place
Our standard doesn’t allow behaviour like this.
Is this model special or it’s a standard?

Incorrect spelling


Incorrect spelling, explanation: standart is a mistaken form, though similar to standard’s French core estandart. In English it was however first used as standhard, from two words stand and hard. Therefore today’s correct form is standard.